Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Reexamination Certificate
2000-07-12
2003-07-01
Cooney, Jr., John M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
C521S114000, C521S115000, C521S116000, C521S117000, C521S118000, C521S129000, C521S155000, C521S159000, C521S167000, C521S170000, C521S174000
Reexamination Certificate
active
06586487
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to the field of polyurethane foams.
BACKGROUND OF THE INVENTION
Automobile bumpers serve the primary purpose of protecting other functional parts of the automobiles upon collision. Automobile bumpers and other effective energy-absorbing devices should be capable of yielding on impact and recovering, either partially or completely, after the impact. Also, such structures must also satisfy size and weight limitations usually imposed by vehicle or other equipment manufacturers as well as any existing or proposed government performance standards.
It is well known in the art that there has been an ongoing need to develop an energy-absorbing polyurethane foam, useful in automobile bumpers, that exhibits both favorable strength properties at relatively lower densities than ordinary polyurethane foams.
It is the object of the present invention to provide a polyurethane material with a combination of such favorable properties.
SUMMARY OF THE INVENTION
The present invention, meeting the above-mentioned need, is directed to a method for making an energy-absorbing foam having a density that is less than about 7 pcf that exhibits excellent strength properties and that is particularly suitable for automobile bumper applications. The method generally involves the steps of reacting (a) a polyisocyanate component selected from the group consisting of polymeric diphenylmethane diisocyanate, mixtures of polymeric diphenylmethane diisocyanate (PMDI) and MDI, and, mixtures of polymeric diphenylmethane diisocyanate and allophanate-modified MDI and/or a urethane-modified MDI (a prepolymer, available as Mondur PF from Bayer Corporation) and (b) a polyol component. The polyol component includes (1) from about 12 to about 45 parts by weight of a diol having a molecular weight that is less than 300; (2) a crosslinker component having a functionality that is greater than 2, a molecular weight ranging from about 92 to about 1000, wherein the OH equivalent of the diol to the OH equivalent of the crosslinker is from about 1 to about 10; (3) from about 40 to about 75 parts of a polyether component having a functionality of from about 1.5 to about 3.5 and a molecular weight of from about 2000 to about 12,000; (4) from about 0.1 to about 3.0 parts of a cell-opening surfactant; and (5) from about 1 to about 3 parts water, based on 100 parts of the polyol component, wherein the amounts of components 1), 2), 3) and 4) total 100 parts. These and other features, aspects, and advantages of the present invention will become better understood with reference to the following description and appended claims.
DESCRIPTION OF THE INVENTION
The polyisocyanates which may be used in the present invention are modified and unmodified polyisocyanates which are well known to those skilled in the art. Generally, the polyisocyanate component includes polymeric diphenylmethane diisocyanate (polymeric MDI). Preferably, the polyisocyanate component includes mixtures of polymeric MDI and other isocyanates selected from the following: 4,4′-diphenylmethane diisocyanate (MDI), mixtures of 4,4′- and 2,4′-diphenylmethane diisocyanate, modified diphenyl diisocyanate prepolymers, including allophanate-modified MDI. The NCO functionality of these isocyanates generally ranges from at least 2. In one embodiment, the isocyanate component has an NCO functionality that ranges from about 2.3 to about 2.7. These isocyanates are well known and available from commercial vendors such as Bayer Corporation. The polyisocyanate component is generally present in an amount such that the NCO:OH index is at least about 0.8.
The polyol component generally includes from about 12 to about 45 parts by weight of a diol having a molecular weight that is less than 300. Mixtures of different compounds containing two hydroxyl groups and having molecular weight of less than about 300 may also be used. Examples of such low molecular weight compounds are ethylene glycol, 1,2- and 1,3-propylene glycol, 1,4- and 2,3-butylene glycol, 1,5-pentane. diol, 1,6-hexane diol, 1,8-octane diol, neopentyl glycol, 1,4-bis-hydroxy-methyl cyclohexane, 2-methyl-1,3-propane diol, dibromobutane diol (U.S. Pat. No. 3,723,392), diethylene glycol, dipropylene glycol. 2-Methyl-1,3-propane diol is a preferred diol.
The crosslinker component of the polyol component generally has a functionality that is greater than 2, a molecular weight ranging from about 92 to about 1000, such that the OH equivalent of the diol to the OH equivalent of the crosslinker is from about 1 to about 10. Examples of suitable crosslinkers include known polyols such as glycerol, trimethylol-propane, 1,2,6-hexanetriol, 1,2,4-butanetriol, trimethylolethane, as well as appropriate hydroxyl-containing polyethers, polyesters, polyacetals, polycarbonates, polyesterethers, polythioethers, polyamides, polyesteramides, polysiloxanes, polybutadienes, and polyketones. A preferred crosslinker includes a propylene oxide/ethylene diamine adduct having an OH number of from about 450 to about 850.
The polyether component includes a polyether, or a mixture of polyethers, that are generally present in an amount ranging from about 40 to about 75 parts and has a functionality of from about 1.5 to about 4 and a molecular weight of from about 2000 to about 8000. These polyethers may be formed as the reaction product of one or more alkylene oxides, such as ethylene oxide, propylene oxide, butylene oxide, or mixtures of two or more such oxides, with an active hydrogen-containing initiator having a functionality of 2 or more. A non-limiting example of a commercially-available diol that may be used as the first polyol in accordance with the present invention includes MULTRANOL 9111, available from Bayer Corporation.
The silicone cell-opening surfactants, which are used in amounts of from about 0.1 to about 3 parts, are known in the art. Polyether siloxanes are particularly suitable silicone cell-opening surfactants. These compounds generally have a polydimethyl siloxane group attached to a copolymer of ethylene oxide and propyene oxide. Examples of useful cell-opening silicone surfactants include those sold as L-3801 and L-3802 from WITCO.
Preferably, the surfactants of the present invention have the generalized average formula M*D
x
D″
y
M* in which
M* is (CH
3
)
3
SiO
1/2
or R(CH
3
)
2
SiO
1/2
;
D is (CH
3
)
2
SiO
2/2
;
D″ is (CH
3
)(R)SiO
2/2
;
x is 81-220, y is 8-40 and D/(D″+M″)≦10 (in which M″ is R(CH
3
)
2
SiO
1/2
);
R is a polyether-containing substituent derived from a blend of certain polyethers selected from two different, groups such that the average molecular mass is 1100-1800. Such surfactants generally have an average molecular weight that is more than about 9,000 and a silicone-polyoxyalkylene oxide copolymer that is composed of two polyethers. Such surfactants are known and can be prepared in accordance to the method discussed in U.S. Pat. No. 5,489,617, incorporated herein by reference in its entirety.
The reaction mixture also contains at least one tertiary amine catalyst for catalyzing the reaction between isocyanate groups and hydroxyl groups (i.e., a urethane catalyst) in an amount of from about 0.2 to about 3 parts. These catalysts are, generally known and include tertiary amines such as triethylamine, tributylamine, N-methylmorpholine, N-ethyl-morpholine, N-coco-morpholine, N,N,N′,N″-tetramethyl-ethylene-diamine, 1,4-diaza-bicyclo-(2,2,2)-octane, N-methyl-N′-dimethyl-amino-ethylpiper-azine, N,N-dimethylbenzylamine, bis-(N,N-diethyl-aminoethyl)-adipate, dimethyl ethanolamine, the formic salt of bis dimethylamino ethyl ether, N,N-diethylbenzylamine, pentamethyldiethylenetriamine, N,N-dimethyl-cyclohexylamine, N,N,N′,N′-tetramethyl-1,3-butanediamine, N,N-dimethyl-&bgr;-phenylethylamine, 1,2-dimethylimidazole, 2-methylimidazole and the like. Also useful are the commercially available tertiary amines such as Niax A1 and Niax A107, available from WITCO; Thancat DD, available from Texaco; a
Bushmire Alan D.
Nodelman Neil H.
Slack William E.
Steppan David D.
Bayer Corporation
Cooney Jr. John M.
Eyl Diderico van
Gil Joseph C.
Mrozinski, Jr. John F.
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