Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Patent
1997-05-28
1999-10-26
Gorr, Rachel
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
524777, 524788, 524791, 1563314, C08G 1828
Patent
active
059730650
DESCRIPTION:
BRIEF SUMMARY
This invention relates to retarded uncatalyzed and catalyzed polyurethane compositions having stable reactivity and to their use for adhesives, sealants and casting compounds.
BACKGROUND OF THE INVENTION
One-component and multiple-component polyurethane compositions have long been used as adhesives, sealants or casting compounds. These applications for polyurethane compositions are reviewed, for example, in Chapters 8 and 11 of Kunststoff-Handbuch, 3rd Edition, Vol. 7, Hanser-Verlag, 1993. In the case of two-component systems, one component generally consists of liquid polyhydroxy compounds optionally containing fillers, catalysts and other auxiliaries while the second component essentially contains a liquid diisocyanate or polyisocyanate either in pure form or as a so-called quasi-prepolymer or in the form of isomer mixtures. By virtue of their good adhesion properties on various materials and their high tensile, tensile shear and peel strengths, coupled with very high breaking elongation, these adhesives, sealants and casting compounds are used in a number of industrial and manual applications, including for example car manufacture, general utility vehicle manufacture, ship building and boat building, general machine construction, the electrical industry and civil engineering.
In many applications, the steps involved require very long pot lives which, in addition, are expected to remain constant over the period for which the polyurethane compositions are stored before application.
The pot life of a polyurethane composition is understood to be the time left for proper application after complete mixing of a two-component of multiple-component system before the viscosity of the mixture becomes so high through incipient reaction that the mixture can no longer be properly applied.
Pot life can be controlled within certain limits through the type and quantity of catalyst used. However, it has not yet been possible for a given formulation to prolong the reaction and hence the pot life any further without a catalyst. In cases such as these, less reactive isocyanates had to be used. It has often been proposed in the general literature and in the patent literature to retard the uncatalyzed reaction by addition of an acid, cf. for example J. H. Saunders, K. C. Frisch, Polyurethanes, Chemistry and Technology, Vol. 1, Chemistry, page 213, Interscience Publ., 1962. For example, the addition of hydrochloric acid or acid chlorides is proposed. However, where this approach is adopted, the reaction is not genuinely retarded, instead all the catalytically active alkaline impurities in the composition are neutralized. However, the addition of acids to adhesives, sealants or casting compounds can lead to corrosion on the surfaces of the substrates to be bonded or encapsulated so that, in many cases, this method cannot be applied.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
Not applicable.
DETAILED DESCRIPTION OF THE INVENTION
Accordingly, the problem addressed by the present invention was to reduce the reactivity of one-component and, preferably, two-component or multiple-component polyurethane compositions below the so-called "basic reactivity" of the composition, i.e. below the reactivity which the composition has without a catalyst. In addition, the pot life directly related to this reactivity was to remain substantially constant throughout the storage of the unmixed components.
According to the invention, the solution to this problem is characterized in that the one-component or multiple-component polyurethane compositions contain partly coated.
In the context of the invention, a "highly disperse silica" is understood to be a fine-particle, substantially amorphous pyrogenic silica with an SiO.sub.2 content of more than 99.8% by weight which is obtained, for example, by hydrolysis of silicon tetrachloride in an oxyhydrogen flame. These silicas are commercially available, for example, under the name of "Aerosil.RTM.".
The addition of highly disperse silicas to adhesives, sealants or casting compounds has
REFERENCES:
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patent: 4251427 (1981-02-01), Recker et al.
patent: 4474900 (1984-10-01), Dominguez
patent: 4742087 (1988-05-01), Kluth et al.
patent: 5127973 (1992-07-01), Sengupta et al.
patent: 5473043 (1995-12-01), Maki et al.
Kunststoff-Handbuch, 3rd Edition, vol. 7, Hanser-Vertag (1993), Chapter 8 and Chapter 11, pp. 417-516 and 643-663.
Polyurethanes, Chemistry and Technology, Part. 1, Chemistry, (1962) p. 213.
Plutniok Claudia
Schlingloff Nicole
Thiele Lothar
Gorr Rachel
Grandmaison Real J.
Henkel Kommanditgesellschaft auf Aktien
Jaeschke Wayne C.
Szoke Ernest G.
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