Organic compounds -- part of the class 532-570 series – Organic compounds – Four or more ring nitrogens in the bicyclo ring system
Reexamination Certificate
1999-05-14
2002-07-30
Sergent, Rabon (Department: 1711)
Organic compounds -- part of the class 532-570 series
Organic compounds
Four or more ring nitrogens in the bicyclo ring system
C252S182200, C252S182210, C252S182220, C528S049000, C528S055000, C528S067000, C528S073000, C560S025000, C560S026000, C560S115000, C560S158000, C560S166000, C560S330000, C560S336000, C560S355000, C564S044000, C564S045000
Reexamination Certificate
active
06426414
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to polyether-modified, water dispersible polyisocyanate mixtures and to a process for their preparation.
2. Description of the Prior Art
Water dispersible polyisocyanates are gaining increasing importance for various fields of use. Water dispersible polyisocyanates play a particular role as crosslinker components for water dilutable two-component polyurethane (2K PU) paints. In combination with aqueous polyol dispersions, they allow the formulation of solvent-free paint systems which are curable at room temperature and provide high-quality coatings which are not inferior to conventional paints with regard to solvent resistance, chemical resistance and mechanical stability. Examples of these compositions are described, e.g., in EP-A 358,979, EP-A 469,389, EP-A 496,210, EP-A 542,105, EP-A 543,228, EP-A 562,282, EP-A 562,436, EP-A 583,728, DE-A 4,129,951, DE-A 4,226,242, DE-A 4,226,243 or DE-A 4,226,270.
Water dispersible polyisocyanates are also of importance as additives e.g. for aqueous adhesive dispersions. They can be used to considerably increase the heat stability and resistance to water of different glued materials as described, e.g., in EP-A 61,628 and EP-A 206,059.
Water dispersible polyisocyanates are also used as crosslinkers for aqueous dispersions in textile treatment (EP-A 560 161 or WO 95/30045) or in formaldehyde-free textile free printing inks (EP-A 571,867 or DE-A 19,533,218). They are also suitable as additives for wet strength treatment of paper (EP-A 564,912, EP-A 582,166. EP-A 707,113, WO 96/20309 and WO 97/04169).
Nonionic polyisocyanates hydrophilically modified with polyethers have found acceptance for all these fields of use in practice. The preparation of such water dispersible polyisocyanates is described in a number of publications.
According to the teachings of DE-A 2,415,435, for example, urethanes from organic, in particular aromatic polyisocyanates and polyethylene glycol monoalkyl ethers containing at least 5 ethylene oxide units are surface-active substances which, according to GB-PS 1,444,933 and DE-A 2,908,844, allow the preparation of stable aqueous emulsions of aromatic polyisocyanates.
Aromatic polyisocyanates hydrophilically modified by reaction with alkylene oxide polyethers are also known from EP-A 61,628 and 95,594. These products are used in the form of aqueous emulsions in particular in the adhesives sector.
Water dispersible formulations of (cyclo)aliphatic polyisocyanates are known, e.g., from EP-A 206,059. They are based on the reaction products of polyisocyanates with mono- or polyhydric polyalkylene oxide alcohols containing at least one polyether chain containing at least 10 ethylene oxide units, and also serve as additives for aqueous adhesives.
EP-A 516,277 describes the hydrophilic modification of special polyisocyanates containing tertiary isocyanate groups by reaction with monofunctional polyalkylene oxide polyethers and the use of these products as crosslinkers for aqueous coating compositions.
For high quality light-fast paints, the polyisocyanate mixtures, which are described in EP-B 540,985 and U.S. Pat. No. 5,200,489 and obtainable by the urethanization of aliphatic and/or cycloaliphatic lacquer polyisocyanates with short-chain polyethylene oxide polyether alcohols containing an average of less than 10 ethylene oxide units, have proved suitable.
The water dispersible polyisocyanates, which are based on 2,4(6)-diisocyanatotoluene (TDI) or mixtures of TDI and 1,6-diisocyanatohexane (HDI) and are known from EP-A 645,410 and EP-A 680,983 as crosslinking agents for aqueous wood and furniture paints, also contain urethanes from polyisocyanate and monofunctional polyethylene oxide polyether alcohols as hydrophilic components.
In addition to these purely nonionic, hydrophilic polyisocyanates containing polyether-urethanes, polyether-modified water dispersible polyisocvanates which additionally also contain ionic groups are also known, e.g., those containing sulfonate groups (cf. e.g. EP 703,255) or amino or ammonium groups (cf. e.g. EP-A 582,166 and EP-A 707,113), and may be used to improve the emulsifiability or to achieve special effects. Such ionically
onionically modified polyisocyanates are generally less suitable for paint uses. They are preferably employed in environment-friendly textile treatment or as wet strength agents for paper.
In spite of their very diverse uses, the water dispersible polyisocyanates of the prior art modified with polyether-urethanes have a number of disadvantages. The water dispersible polyisocyanates, which have been prepared using higher molecular weight polyether alcohols (e.g., those having an average molecular weight of approx. 700 in the case of pure polyethylene oxide polyethers), often can only be incorporated homogeneously into aqueous media using considerable shear forces (e.g., high-speed stirrers) because of a very high viscosity maximum which has to be overcome during the dispersing step. Also, such products often tend to crystallize, especially at the high emulsifier contents that are necessary to achieve particularly finely divided, sedimentation-stable dispersions.
Water dispersible polyisocyanates, which can be stirred manually very easily into water to give stable dispersions and show no tendency to crystallize even at high degrees of hydrophilic modification, i.e. at high contents of ethylene oxide units, can be obtained using shorter polyether chains. However, because of the relatively low molecular weight of the polyalkylene oxide polyethers employed for the modification, both the content of isocyanate groups and the average isocyanate functionality decrease constantly with the increasing degree of hydrophilization. In practice it is precisely these highly hydrophilic polyisocyanates with high NCO contents and the highest possible functionality, which are desired for the majority of the previously mentioned fields of use, for example, as crosslinkers for paints and coatings.
Therefore, an object of the present invention is to provide new water dispersible polyisocyanate mixtures which are suitable for use in the previously mentioned applications for hydrophilic polyisocyanates, in particular as starting components for the preparation of polyurethane plastics, and above all as crosslinking agents for aqueous binders in coating compositions, and which do not have the disadvantages mentioned for the water dispersible polyisocyanates of the prior art.
This object may be achieved with the polyisocyanate mixtures according to the invention and the process for their preparation. The polyisocyanate mixtures according to the invention are based on the surprising observation that the reaction of low monomer-containing polyisocyanates prepared from at least two diisocyanate molecules with monofunctional polyethylene oxide polyether alcohols under allophanate-forming conditions gives water dispersible polyisocyanate mixtures which can already be stirred considerably more easily and in a more finely divided form into aqueous systems at significantly lower degrees of hydrophilic modification than the prior art water dispersible polyisocyanates which have been prepared using polyether alcohols of identical construction and in which the polyether chains are linked to the polyisocyanate via urethane bonds.
The process according to the invention allows the preparation of hydrophilic polyisocyanates which are stable to crystallization and are distinguished by a higher content of isocyanate groups and a higher functionality, coupled with the same or an even better water dispersibility, when compared with the known polyisocyanate mixtures containing polyether chains.
EP-A 000,194, EP-A 303,150, EP-A 682,012, U.S. Pat. No. 5,380,792 and U.S. Pat. No. 5,086,175, which are directed to the preparation of polyisocyanates containing allophanate groups, disclose the use of the known polyether alcohols as suitable alcoholic starting compounds for the preparation of such products. In addition, EP-A 000,194, EP-A 303,15
Halpaap Reinhard
Laas Hans-Josef
Wamprecht Christian
Roy Thomas W.
Sergent Rabon
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