Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1999-04-29
2001-11-27
Michl, Paul R. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C528S499000
Reexamination Certificate
active
06323261
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a method and apparatus for producing a chlorinated rubber. More specifically, it relates to a method and apparatus for efficiently producing a chlorinated rubber from a chlorinated rubber cake obtained by chlorinating an acidic or highly acidic rubber latex maintaining high quality.
BACKGROUND ART
Since chlorinated rubber obtained by chlorinating natural rubber or a polyisoprene rubber such as synthetic isoprene has excellent acid resistance, alkaline resistance, chemical resistance, flame resistance and conductivity as well as a film forming capability, it is used in varnishes, paints, printing ink vehicles, wrapping films, adhesives etc. In particular, a highly chlorinated product having a chlorine content of 55% by weight or more is widely used as a material for anti-corrosion paints having excellent drying properties.
Conventionally, as a method for chlorinating a polyisoprene rubber, a method consisting of obtaining powders by dissolving a polyisoprene rubber in a chlorinated hydrocarbon solvent, then blowing in a chlorine gas for reaction, and then evaporating the chlorinated hydrocarbon by a spray dry method is known. This method is widely used since it can chlorinate a polyisoprene rubber homogeneously and obtain a highly chlorinated rubber soluble in an organic solvent. However, in view of recent movements for global environmental conservation, the use of chlorinated hydrocarbon solvents (carbon tetrachloride) is expected to be limited.
Hence, development of a method for dispersing and chlorinating a polyisoprene rubber in an aqueous medium is increasingly desired. Accordingly, the present inventors proposed a technique for obtaining a chlorinated rubber by supplying a chlorine gas to a highly acidic aqueous rubber latex as disclosed in Japanese Patent Laid-Open No. 5-202101.
The chlorination method disclosed in Japanese Patent Laid-Open No. 5-202101 is a method of blowing a chlorine gas into a polyisoprene-containing highly acidic aqueous rubber latex, more specifically, it is a method of placing highly concentrated hydrochloric acid in a reaction vessel, cooling, introducing chlorine while stirring under ultraviolet ray irradiation, and dropping a polyisoprene rubber latex with a surfactant dispersed therein for chlorination.
Nevertheless, it was found that the chlorinated rubber slurry obtained by this chlorination method has characteristics unlike conventional ones. That is, since it easily adheres to the wall portion of a drying device when drying a chlorinated rubber cake obtained by filtrating the chlorinated rubber slurry, and easily forms a large agglomerate, the drying efficiency in a conventional drying method is extremely poor. For example, a pneumatic drier is used for drying cake-like powders, but since the above-mentioned chlorinated rubber cake adheres to the wall portion, a drying air flow cannot be applied thereto.
In the case where a chlorinated rubber is utilized in inks, paints, or adhesives, the molecular weight thereof needs to be controlled. However, there is a risk that the molecular weight will change unless the production process for the chlorinated rubber cake is finished in a short time.
Further, in order to prepare a chlorinated rubber cake from a chlorinated rubber slurry, for example, a centrifugal separator is used. However, since the chlorinated rubber obtained by the above-mentioned method has extremely small particles, the filtration property becomes remarkably poor when the thickness of the cake accumulated in the centrifugal separator becomes about 30 mm or more so that, when washing with water is included, a long time consuming operation is required for one cycle, and thus molecular weight change is liable to occur. Moreover, the water content of the chlorinated rubber cake needs to be adjusted to within 45 to 65% since the cake becomes hard with a water content of 40% or less.
Further, since a chlorinated rubber slurry is collected from a highly acidic aqueous medium, it limits the material of the centrifugal separator.
DISCLOSURE OF INVENTION
Accordingly, an object of the present invention is to provide a method and apparatus for producing a high quality chlorinated rubber from an acidic or highly acidic chlorinated rubber cake obtained by chlorinating a rubber latex or a water dispersion thereof efficiently and with easy handling.
The present inventors conducted intensive study to solve the above-mentioned problems.
That is, the present invention provides a method for producing a chlorinated rubber comprising fluidized drying an acidic or highly acidic chlorinated rubber cake obtained after chlorinating a rubber latex or an aqueous dispersion with a drying medium to obtain preliminary dried powder, and fluidized drying of the preliminary dried powder again.
Further, the present invention provides an apparatus for producing a chlorinated rubber equipped with an (A) unit comprising a fluidized drying means using a medium (hereinafter referred to as “fluidized medium drying means”) having a supply opening for a chlorinated rubber cake, and containing a drying medium in an inside portion thereof,
a bag filter connected with the fluidized medium drying means via a conduit, and
a fluidized drying means provided downstream of the bag filter.
Furthermore, the present invention provides an apparatus for producing the chlorinated rubber, comprising a (B) unit upstream of the (A) unit, the (B) unit being an apparatus for producing a chlorinated rubber cake from a chlorinated rubber slurry obtained after chlorinating a rubber latex or an aqueous dispersion, comprising:
a belt filter which is movable in the horizontal direction, and
a means for suctioning water contained in the chlorinated rubber slurry via the belt filter.
Still further, the present invention provides an apparatus for producing the chlorinated rubber comprising the (B) unit upstream of the (A) unit, and further comprising a (C) unit upstream of the (B) unit, the (C) unit being an apparatus for producing a chlorinated rubber slurry obtained by chlorinating a rubber latex or an aqueous dispersion, comprising:
a reaction vessel for accommodating the reaction liquid, provided with an outlet portion for the reaction liquid,
a circulating line for guiding the reaction liquid from the outlet portion to outside of the reaction vessel, and returning it back to the reaction vessel,
a heat exchanger provided at at least one point in the circulating line, and
a UV lamp provided in the reaction vessel and/or the circulating line.
REFERENCES:
patent: 3677321 (1972-07-01), Felstead
patent: 3932370 (1976-01-01), Landi
patent: 4358901 (1982-11-01), Takabatake
patent: 4430483 (1984-02-01), Alfes
patent: 5336332 (1994-08-01), Satoh
patent: 6058624 (2000-05-01), Bach
patent: 0 545 593 (1993-06-01), None
patent: 53-11988 (1978-02-01), None
patent: 1-299637 (1990-12-01), None
Hisano Jun-ichi
Janado Tadashi
Konishi Masanori
Kurita Naoyasu
Nakano Shinji
Asahi Denka Kogyo K.K.
Michl Paul R.
Sughrue Mion Zinn Macpeak & Seas, PLLC
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