Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From reactant having at least one -n=c=x group as well as...
Reexamination Certificate
1999-08-13
2001-10-02
Gorr, Rachel (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From reactant having at least one -n=c=x group as well as...
C521S170000, C521S917000, C264S051000, C264S328800, C425S81700C, C422S131000
Reexamination Certificate
active
06297342
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a process for the production, without a stirring apparatus, of a polyurethane-forming reaction mixture from an isocyanate and a polyol formulation, wherein these two components are fed to a mixing zone and are mixed with one another therein, and wherein at least one of the components has a viscosity greater than 3000 mPa.s, preferably greater than 5000 mPa.s.
BACKGROUND OF THE INVENTION
New fields of application require the processing of polyol formulations of higher viscosity. The use of components of higher viscosity offers many advantages. In general the viscosity of polyether polyols, and in particular polyester polyols, increases distinctly with increasing functionality. In order to achieve high degrees of cross-linking, and thus a better mechanical property level, the use of relatively larger quantities and constituents of polyol components of high functionality is desirable.
As high-viscosity component, the isocyanate component is also used in the form of a prepolymer.
Satisfactory mixing in a self-cleaning mixing chamber comprising no stirring apparatus still presents difficulties to the extent to which the viscosity of such components increases. Page 175, last paragraph of the “Kunststoff-Handbuch”, Vol. 7, “Polyurethanes” (published by Carl Hanser Verlag, Munich 1993), states: “Whereas the miscibility limit was previously reached at 1500 mPa.s, it is currently possible to handle viscosities exceeding 2000 mPa.s in accordance with the injection method”. In reality, however, it has not yet been possible to process reaction components with viscosities above 3000 mPa.s in accordance with the counterflow high-pressure injection method. The resultant foam contains striations and the physical values fall rapidly. It has therefore been necessary to use mixing heads comprising stirring apparatus.
It was also known (“Kunststoff-Handbuch, p. 125) to reduce the viscosity at an elevated processing temperature to 2000 to 3000 mPa.s. However, the increased component temperature causes the reactivity of the systems to increase such that the foaming process can no longer be controlled.
Where the following observations relate to the polyol component as high-viscosity component, this is by way of example. The observations apply correspondingly when an isocyanate component is used as high-viscosity component.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a process and a mixing head with which it is possible, without using a stirring apparatus, to produce a reaction mixture of the type referred to in the introduction which reacts to form a high quality product.
This object is achieved in that a polyol formulation having a viscosity of at least 3000 mPa.s is fed into the mixing zone at low pressure and in that at least two streams of low-viscosity components (isocyanate and optionally low-viscosity polyol) are injected at high pressure into the stream of high-viscosity polyol formulation.
Surprisingly, this results in a good mixing of components of higher viscosity. The invention makes use of the fact that, as a result of the splitting of the higher-viscosity component into two or more sub-streams, although a shift occurs in its energy, the energy is increased overall.
REFERENCES:
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patent: 4426348 (1984-01-01), Salisbury
patent: 4608233 (1986-08-01), Fiorentini
patent: 5270013 (1993-12-01), Decker
patent: 5277567 (1994-01-01), Bauer et al.
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Patent Abstract of Japan, vol. 04, No. 187, Dec. 23, 1980—JP 55-133938 (ASAHI Glass Co. Ltd.
Kunststoff-Handbuch, Band 7: Polyurethane: Carl Hanser Verlag München Wien 1983, p. 175 Das Mischermodell.
Kunststoff-Handbuch, Band 7: Polyurethane, Carl Hanser Verlag München Wien 1983, p. 125 Prinzipieller Aufbau von Maschinen und Anlagen.
Friederichs Wolfgang
Krippl Kurt
Künzel Uwe
Schulte Klaus
Weber Hans-Ulrich
Bayer Aktiengesellschaft
Cheung Noland J.
Gil Joseph C.
Gorr Rachel
Sloane Carolyn M.
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