Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Reexamination Certificate
2002-01-15
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...
C521S125000, C521S126000, C521S127000, C521S128000, C521S129000, C521S130000, C521S159000, C521S170000, C521S174000
Reexamination Certificate
active
06586486
ABSTRACT:
The present invention relates to a process for the preparation of low-density hydrophilic flexible polyurethane foams by reacting organic and/or modified organic polyisocyanates (a) with a specific polyetherol mixture (b) and, if required, further compounds (c) having hydrogen atoms reactive toward isocyanates, in the presence of water and/or blowing agents (d), catalysts (e) having a specific gel catalyst/blowing catalyst ratio and, if required, further assistants and additives (f).
The preparation of flexible polyurethane foams by reacting organic and/or modified organic polyisocyanates or prepolymers with compounds having a higher functionality and at least two reactive hydrogen atoms, for example polyoxyalkylenepolyamines and/or preferably organic polyhydroxy compounds, in particular polyetherols, having molecular weights of from 300 to 6000, and, if required, chain extenders and/or crosslinking agents having molecular weights of up to 400, in the presence of catalysts, blowing agents, flameproofing agents, assistants and/or additives, is known and has been widely described. A review of the preparation of flexible polyurethane foams is given, for example, in Kunststoff-Handbuch, Volume VII, Polyurethane, 1st Edition 1966, edited by Dr. R. Vieweg and Dr. A. Höchtlen, and 2nd Edition, 1983, and 3rd Edition, 1993 edited in each case by Dr. G. Oertel (Carl Hanser Verlag, Munich).
Water is preferably used as the blowing agent, particularly in the case of flexible polyurethane foams. In the reaction with the corresponding isocyanates, ureas form and are to a large extent responsible for rigidity-determining properties. It is understandable and obvious that in particular the method of water addition and the amount of water used are of great importance for the foam properties.
EP-A-793681 describes the preparation of flexible foams. First, an NCO prepolymer having an NCO content of from 3 to 15% by weight is prepared using a polyol which comprises at least 50% of ethylene oxide units. The amount of water used accounts for from 1.5 to 5 times the amount of prepolymer, based on weight. In order to produce the foam, the water used must additionally be at least from 10 to 50° C. warmer than the NCO prepolymers. This requires complicated technological steps.
WO-A-9534591 uses a specific prepolymer composition which consists of two substantial components. A prepolymer having an NCO content of from 5 to 15% by weight is produced by reaction with a flexible-foam polyol (ethylene oxide content from 5 to 25%) and said prepolymer is combined, in the polyurethane formation, with a second isocyanate component (not prepolymerized) having an NCO content of from 30 to 33% by weight. This is said to contribute toward better processibility of the highly viscous prepolymer. From 2 to 8 parts of water are used. The polyol component used in addition to the polyol employed in the prepolymer is an ethylene oxide-rich polyol (>80% of ethylene oxide), in amounts of from 5 to 25 parts by weight.
U.S. Pat. No. 4,144,386 claims the preparation of low-density foam by using a combination of blowing agents. In addition to relatively high water contents, in particular relatively large amounts of CFCs are used. This route is prohibited for environmental protection reasons.
U.S. Pat. No. 4,137,200 describes the reaction of an NCO prepolymer mixture, consisting of a prepolymer based on polyethylene glycol and a prepolymer based on a flexible-foam polyol, and unreacted isocyanates and large amounts of water, to give a flexible slabstock foam, it being necessary to cool down the water used by mixing in ice.
In WO-A-9616099, U.S. Pat. No. 5,591,779 and EP-A-894814, large amounts of water are reacted with an NCO prepolymer (from 3 to 15% by weight of NCO, based on ethylene oxide-rich polyols), it being necessary for the temperature of the reacted water to be from 10 to 50° C. above the temperature of the prepolymer, which complicates the preparation process. Superabsorbers are used as process additives.
WO-A-9429361 (EP-A-707607) describes the use of a prepolymer (>85% of 4,4′-MDI) having an NCO content of from 5 to 10%, which was obtained by reaction with an ethylene oxide-rich flexible-foam polyol. Foaming is effected with water contents of >20 parts per 100 parts of prepolymer.
DE-A-3819940 claims TDI foams, hexamethylene diisocyanate foams and isophorone diisocyanate foams, which are each prepared by foaming the pure isocyanates with water at low indices.
EP-A-346670 discloses a process for the preparation of flexible foams using high water contents. Here, specific TDI mixtures, frequently containing TDI 65, in addition to hexamethylene diisocyanate and isophorone diisocyanate, are claimed, indicating that this process is unsuitable for MDI-containing isocyanates. Mixtures of random ethylene oxide/propylene oxide polyetherols are used as polyols.
WO-A-9534589 is based on the use of an isocyanate combination. The crystallization problems of the 4,4′-MDI-rich NCO components are evidently supposed to be overcome by prepolymerization. An isocyanate mixture having a higher functionality is also used. Low-density flexible slabstock foams are produced.
WO-A-9606874 claims water-blown flexible foams, a monofunctional polyether alcohol having high ethylene oxide contents being required as a process assistant. Up to 10 parts of water are said to be capable of being processed using the system. However, the use of monofunctional components is disadvantageous for the level of properties.
In U.S. Pat. No. 4,110,508, NCO prepolymers based on polyethylene glycols are reacted at a water index of from 4000 to 40000 in order thereby to produce foam-textile composites in which the foam does not penetrate into the textile material.
U.S. Pat. No. 4,365,025 describes the reaction of an NCO prepolymer comprising ethylene oxide-rich polyols and a polyisocyanate with water. Owing to the low NCO content, the prepolymers used have a high viscosity and are in fact diluted with the polyisocyanate. Owing to the stabilizers used, the foaming process is difficult to control.
DE-A-3721056 describes cold-curing flexible foams which are produced using high water contents at an index of <70. Owing to the relatively low content of ethylene oxide in the polyols used, mixing problems are to be expected with the high water content.
EP-A-392788 claims the production of NCO prepolymers having an NCO content of from 2 to 12% by weight, high viscosities being achieved. These prepolymers are reacted with a mixture which comprises 95% of water. Owing to the disadvantageous mixing ratios and the large viscosity differences, these foams are difficult to process.
In EP-A-566247, NCO prepolymers having an NCO content of from 2 to 15% by weight are reacted with a polyol component containing 50% of water. A 1,2-dialkylimidazole is required as a special catalyst.
In WO-A-9719971, the isocyanate component described consists of an NCO prepolymer (NCO content: from 9 to 20% by weight) with an unprepolymerized polymethylenepolyphenylene polyisocyanate (PMDI), if required as a mixture with TDI. From 3 to 15 parts of water are used as a blowing agent. Here too, the mixing with the pure isocyanate component evidently serves for improving the processibility of the isocyanate component.
EP-A-578381 describes a cold-molded foam prepared by reacting an NCO component, consisting of an MDI prepolymer which is subsequently mixed with PMDI, using water as the sole blowing agent. During foaming, a defined excess pressure is applied by means of the mold geometry, in order to obtain satisfactory moldings.
EP-A-769510 once again claims a flexible PU foam preparation by reaction of an NCO prepolymer with an excess of water. The polyol component used in said prepolymer is a flexible-foam polyol having an ethylene oxide content of from 0 to 30% by weight. Owing to the disadvantageous mixing ratios, the foam preparation is to be considered as demanding.
EP-A-547765 describes an isocyanate composition which comprises at least >85% of 4,4′-MDI and is prepared
Falke Peter
Lutter Heinz-Dieter
Pcolinski Michael J.
BASF - Aktiengesellschaft
Borrego Fernando A.
Cooney Jr. John M.
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