Agitating – Stationary deflector in flow-through mixing chamber – Curved deflector surface
Reexamination Certificate
1998-09-23
2001-03-20
Soohoo, Tony G. (Department: 1723)
Agitating
Stationary deflector in flow-through mixing chamber
Curved deflector surface
C366S336000
Reexamination Certificate
active
06203188
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a module for a static mixer for a plastic, flowable, composition to be mixed which is critical with respect to the dwell time. The invention refers further to a corresponding mixer and to uses of the mixer.
2. Description of the Prior Art
In the manufacture of shaped parts of hard PVC, PVC in granulate and/or powder form is mixed with lubricants, stabilizers and other additives and the mixture is then further treated in extruders to form a workable composition. During this, the mixture is heated up and compressed to a suitable working pressure. Twin screw extruders are advantageously employed. The intermediate product thus produced is, however, in a state which is still not sufficiently homogeneous for the manufacture of the shaped parts. Therefore, in many plants static mixers are arranged between the extruders and the molding dies or tools. In these mixers, the mixture is homogenized, and indeed—for the protection of the PVC polymers—at low shear velocities. PVC is, a thermoplast which can be worked above 160° C. It is however, not stable thermally, since hydrogen chloride already segregates at 140° C. In the manufacture of window sections of hard PVC, the plastic is processed at temperatures, between 190 and 200° C. At these temperatures the dwell time in the static mixer is rather critical. The dwell time can turn out to be so long at special locations within the static mixer that discolorations and losses in quality arise. As soon as such unfavorable phenomena set in, they increase very rapidly so that the manufacturing process must be interrupted. The static mixers must be cleaned before the process is continued.
SUMMARY OF THE INVENTION
The object of the invention is to further develop known static mixers in such a manner that more favorable conditions with respect to the dwell time are present and that a cleaning of the static mixer can be performed simply. This object is satisfied by a static mixer which has a modular mixer structure.
The module is a part of a static mixer which is provided for a plastic, flowable, composition to be mixed which is critical with respect to the dwell time. The apparatus comprises a tubular housing in which rods are arranged. The arms are inclined with respect to the longitudinal axis of the housing; they cross each other substantially on a straight line perpendicular to the longitudinal axis. The module comprises a sleeve which can be pushed into the housing. The inner wall of the device which conducts the mixing mass is formed by inner sides of the sleeve. The arms are formed in the shape of rods each having a tip or apex directed opposite to the direction of movement of the composition to be mixed and a base fastened to the inner side of the sleeve in each case. Each tip forms an intermediate space with respect to the inner wall of the device.
The module in accordance with the invention or a mixer assembled from such modules can also be used for the processing of latex/rubber or of another plastic flowable mass of a polymer which is critical with respect to the dwell time.
Other features and advantages of the present invention will be understood upon reading and understanding the detailed description of the preferred exemplary embodiments, found hereinbelow, in conjunction with reference to the drawings, in which like numerals represent like elements.
REFERENCES:
patent: Re. 34255 (1993-05-01), Friedrich
patent: 2669946 (1954-02-01), Peyton
patent: 4049241 (1977-09-01), Taniguchi
patent: 4249877 (1981-02-01), Machen
patent: 4478516 (1984-10-01), Kessler
patent: 4522504 (1985-06-01), Greverath
patent: 4685514 (1987-08-01), Brown
patent: 4692030 (1987-09-01), Tauscher et al.
patent: 5255974 (1993-10-01), Signer
patent: 678284A5 (1991-08-01), None
patent: 254337A1 (1988-02-01), None
patent: 0154013A2 (1985-09-01), None
patent: 2-223405 (1990-09-01), None
Maurer Rudolf
Studlek Joachim
Soohoo Tony G.
Sulzer Chemtech AG
Townsend and Townsend / and Crew LLP
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