Chemical apparatus and process disinfecting – deodorizing – preser – Chemical reactor – Organic polymerization
Patent
1995-10-25
1997-07-29
Bhat, Nina
Chemical apparatus and process disinfecting, deodorizing, preser
Chemical reactor
Organic polymerization
42228, 42229, 366 83, 366 85, 366 88, B29C 4776
Patent
active
056519443
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND AND SUMMARY OF THE INVENTION
The invention relates to an apparatus for degassing thermoplastic synthetic plastics material which is supplied through at least one intake opening into a housing of a first screw section, at the end of which the plasticized synthetic plastics material is pressed into at least one connection channel in which at least one filter for the synthetic plastics material is disposed, from which the synthetic plastics material streams to an upstream opening of a housing of a second screw section which is disposed coaxially to the first screw section and conveys the synthetic plastics material along a degassing region provided with at least one degassing opening to an exit, a sealing section being interposed between the two screw sections which avoids bypassing of the connection channel, the two screw sections and the sealing section being bearingly supported in bores of the housings having equal diameters.
Such an apparatus has become known from a prior suggestion of the inventors (WO 93/04841). This known apparatus enables one to clean thermoplastic synthetic plastics material in plasticized condition by means of the filter and then to degas it, however it is sensitive with respect to disposal of the opening through which the plasticized synthetic plastics material, after having passed the filter, flows into the second screw section. Further, some kinds of synthetic plastics material are only incompletely degassed, inasmuch the synthetic plastics material is subject to turbulences when passing the filter, so that gas inclusions are worked into the interior of the synthetic plastics material rope. Investigations of the applicants have been shown that the problems when degassing are based on the fact that the migration path for the gas bubbles in the degassing region is too long. It is possible to counteract this by operating the screw in the degassing region with a reduced speed so that the synthetic plastics material passes the degassing region comparatively slow. However, this has the disadvantage that the throughput of the apparatus is unsufficient. Another possibility is to make the degassing region comparatively long, what has the disadvantage of a considerable entire length of the apparatus.
The invention has at its object to avoid these disadvantages and to improve degassing at an apparatus of the initially described kind without that the throughput of the apparatus is substantially reduced and without that the constructional length of the apparatus is increased. The invention solves this task by the features that in the housing of the second screw section at least one baffle member for the synthetic plastics material flow is provided between the upstream opening and the degassing openings, which baffle member forces the synthetic plastics material stream into a hose-formed shape and is adjustable with respect to the upstream opening, the baffle member being disposed so in front of the upstream opening that the synthetic plastics material streaming from the upstream opening into the housing of the second screw section hits directly the periphery of the baffle member which is disposed axially spaced apart from the nearest degassing opening and has a cross section tapering towards the second screw section. This baffle member forms a radial gap between its periphery and the inner surface of the housing of the second screw section, which gap as a rule is so narrow that through this gap so to speak a hose-shaped synthetic plastics material film having a small wall thickness is extruded. This hose-shaped synthetic plastics material stream is taken along by the second screw section and is conveyed further in the degassing section, the small wall thickness of this synthetic plastics material film causes a short migration path for the gas bubbles and thereby an efficient degassing, even if the screw revolves with a comparatively high speed. Within this it is of advantage that already filtered synthetic plastics material is supplied to the region of the baffle member, so that f
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Bacher Helmut
Schulz Helmuth
Wendelin Georg
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