Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Reexamination Certificate
2000-04-28
2003-05-27
Sergent, Rabon (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
C521S130000, C521S160000, C521S174000, C521S176000
Reexamination Certificate
active
06569913
ABSTRACT:
The present invention is concerned with new isocyanate-terminated prepolymers made from polyols having a high molecular weight and with the preparation of flexible polyurethane foams using such prepolymers.
U.S. Pat. No. 4,687,851 discloses the preparation of polyurethane and/or polyurea polymers which are the reaction product of a reaction mixture comprising a polyisocyanate and a polyether polyahl having an equivalent weight of at least 2000 and a level of unsaturation of less than 0.1% by weight. The object of this patent was to use high molecular weight polyols having a low level of unsaturation leading to elastomeric and flexible materials having high resilience, excellent tensile properties and compression set and a low glass transition temperature. The use of polyols having a moderate equivalent weight (250-2000) has been disclosed as well; no special directions are given how to use such polyols especially not together with water. All examples relate to the preparation of solid elastomers.
EP-394487 discloses the use of high molecular weight polyether polyols having low unsaturation levels for making flexible foams having a low resonant frequency; preferably such polyols are used as the matrix for so called polymer-dispersed polyols. EP-443614 discloses an improvement of EP-394487: it becomes sometimes hard to satisfactorily mix starting materials in the preparation of a polyurethane foam because of the high viscosity of the polyols; in order to overcome this a viscosity reducing compound having an addition-polymerizable unsaturated group is added in EP-443614, like e.g. a methacrylate type compound, vinylether type compound, a vinylester type compound, an alkylether type compound and an alkylester type compound.
EP-422811 discloses the use of a polyisocyanate for preparing flexible polyurethane foams having good elasticity and elongation properties; the polyisocyanate is a prepolymer made from polyether polyols having a high molecular weight. The NCO content of the prepolymer used is rather high, which means the amount of polyol in the prepolymer is limited.
GB 2296499 discloses the use of a prepolymer composition for producing microcellular molded articles. Although a wide range of polyols have been disclosed for use in the prepolymer composition and the resin side component, there is no special attention given to the use of polyols having a high molecular weight and certainly not to the use of such polyols in the preparation of water blown flexible foams. The amounts of water used are low and products obtained are microcellular elastomers of high density.
EP-420273 is related to a process for making flexible foams using prepolymer compositions in order to make soft foams with a low shore A hardness. No attention is given to the problems encountered when using polyols with a high molecular weight.
EP-485953 is related to improving elongation of flexible foams by using prepolymers made from polyols having a high molecular weight and a relatively high oxyethylene content.
WO 95/18163 is related to the preparation of rigid polyurethane foams using a prepolymer made by reacting polymeric MDI and a polyol having a molecular weight of at least 2000 and a relatively high oxyethylene content.
EP-392788 is related to isocyanate-terminated prepolymers and the use of them in making flexible foams. The prepolymers used have been made from polyols having a relatively low molecular weight and in preparing a flexible polyurethane foam a resin-side is used which does not contain polyol.
It is known that polyols having a high molecular weight have a higher viscosity than polyols having a low molecular weight. In EP-443614 it was recognised that such high viscosity could lead to processing difficulties; these difficulties were diminished by adding a viscosity reducing compound.
EP-111121, EP-344551, WO95/34589, WO95/34590 and WO95/34591 further disclose the use of prepolymers for preparing flexible foams; no special directions are given as to the use of polyols having a high molecular weight.
When higher amounts of high molecular weight polyols are used the processing difficulties would be more pronounced. It was found that in the preparation of MDI (diphenylmethane diisocyanate)-based, water-blown flexible polyurethane foams the viscosity of the mixture of the water and the polyol increased in the same way as the viscosity of the polyol, with increasing molecular weight. Surprisingly it was found that the viscosity of a prepolymer did not give rise to a viscosity commensurate with the viscosity of the polyol used; the viscosity of a prepolymer containing a high amount of a polyol having a high molecular weight was only slightly higher than the viscosity of a prepolymer made from a high amount of a polyol having a lower molecular weight despite the fact that the viscosity of these polyols differed remarkably. Therefore the present invention is concerned with such prepolymer compositions and with a process for making flexible foams by reacting such prepolymer compositions with an isocyanate-reactive compound or composition using water as blowing agent. The processing is much improved, even in the absence of viscosity reducing agents. The foams show very good properties, in particular a high ball rebound and a low compression set.
Consequently the present invention is concerned with an isocyanate-terminated prepolymer composition comprising 1) a urethane containing adduct of diphenylmethane diisocyanate optionally containing oligomers of it having an isocyanate functionality of more than 2 and of a polyether polyol 1), having an equivalent weight of 2200-10000, an oxyethylene content of 5-30% by weight and an average nominal hydroxyl functionality of 2-4, the amount the polyether moieties being 35-70% by weight and 2) 2 to 15% by weight of unreacted oligomers of diphenylmethane diisocyanate, said oligomers having an isocyanate functionality of at least 3, and/or 1 to 25% by weight of toluene diisocyanate, all amounts being calculated on the total weight of the composition, the composition having an NCO-content of 8-22% by weight when no toluene diisocyanate is present and an NCO-content of 8.5-26% by weight when toluene diisocyanate is present.
Further the present invention is concerned with a process for preparing a flexible polyurethane foam by reacting the above isocyanate-terminated prepolymer composition with a polyether polyol 2) having an equivalent weight of from 1000 to less than 2200 and a nominal functionality of from 2-4 and with water optionally using chain extenders, cross-linkers, auxiliaries and additives.
The above prepolymer composition according to the invention preferably has an NCO content of 10-20% by weight when no toluene diisocyanate is present and of 11-24% by weight when toluene diisocyanate is present, and a viscosity of at most 4500 mPa.sec at 25° C. (Brookfield). The equivalent weight of polyol 1) preferably is 2500-8000 and most preferably 3000-7000; its average nominal functionality is most preferably 3.
In the context of the present invention the following terms have the following meaning:
1) isocyanate index or NCO index or index: the ratio of NCO-groups over isocyanate-reactive hydrogen atoms present in a formulation given as a percentage:
[
NCO
]
×
100
(
%
)
[
active
hydrogen
]
.
In other words the NCO-index expresses the percentage of isocyanate actually used in a formulation with respect to the amount of isocyanate theoretically required for reacting with the amount of isocyanate-reactive hydrogen used in a formulation.
It should be observed that the isocyanate index as used herein is considered from the point of view of the actual foaming process involving the isocyanate ingredient and the isocyanate-reactive ingredients. Any isocyanate groups consumed in a preliminary step to produce modified polyisocyanates (including prepolymers) or any active hydrogens consumed in a preliminary step (e.g. reacted with isocyanate to produce modified polyols or polyamines) are not taken into account in the calculation of t
Chaffanjon Pierre Gilbert Henri Jean
Huygens Eric
Kotaji Shpresa
Stroobants Peter Frans Eugeen Maria
Imperial Chemical Industries PLC
Pillsbury & Winthrop LLP
Sergent Rabon
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