Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Treating polymer containing material or treating a solid...
Patent
1998-05-07
1999-11-30
Merriam, Andrew E. C.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Treating polymer containing material or treating a solid...
528499, 528500, 528501, 528502F, 524546, 524805, 425222, C08J 312
Patent
active
059944994
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a polytetrafluoroethylene granular powder for molding and a preparation process thereof.
BACKGROUND ART
Hitherto a process for granulating a polytetrafluoroethylene granular powder for molding by using an organic liquid and tumbling a powder has been proposed. For example, JP-B-45-9071 discloses a process for tumbling a powder while heating the powder, JP-B-44-22620 discloses a process for granulating by tumbling for obtaining a filler-containing PTFE granular powder, and JP-B-46-14535 discloses a process for granulating by tumbling with a pan type pelletizer.
However, the processes disclosed in those publications have problems such that an organic liquid used is inflammable and harmful to human body and further that equipment cost for carrying out the processes becomes high.
An object of the present invention is to provide a polytetrafluoroethylene granular powder for molding, which contains only a small amount of coarse particles, and a process for preparing the granular powder at high yield with good tumbling efficiency without necessity of using an organic liquid.
DISCLOSURE OF THE INVENTION
The present invention relates to a process for preparing a polytetrafluoroethylene granular powder for molding by granulating a polytetrafluoroethylene powder through tumbling with a granulator having a rotating disc and a rotating side plate; characterized in that the granulator: provided on the periphery of the disc, together, and a vortex of the polytetrafluoroethylene powder which is caused by tumbling, polytetrafluoroethylene powder wetted with an aqueous solution containing a surfactant.
Also the present invention relates to a process for preparing a polytetrafluoroethylene granular powder for molding by granulating a polytetrafluoroethylene powder through tumbling with a granulator having a rotating disc and a rotating side plate; characterized in that the granulator: provided on the periphery of the disc, the periphery of the disc, and a vortex of the polytetrafluoroethylene powder which is caused by tumbling, polytetrafluoroethylene powder wetted with an aqueous solution containing a surfactant.
Further the present invention relates to a polytetrafluoroethylene granular powder for molding which is obtained by any of the above-mentioned processes and characterized in that an apparent density of the granular powder is not less than 0.6 g/ml, flowability of the granular powder is not less than 6 times and an average particle size of particles in the granular powder is from 400 to 1,000 .mu.m.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a cross-sectional and partly broken view for explaining the granulator with a rotating inclined disc and a rotating side plate, which is used in Experimental Examples 1 to 4.
FIG. 2 is a diagrammatical view when looking, from above, inside of the granulator with a rotating inclined disc and a rotating side plate, which is used in Experimental Examples 1 to 4.
FIG. 3 is a cross-sectional view of the rotating disc type granulator, which is used in Experimental Examples 5 to 8.
FIG. 4 is a cross-sectional view of the rotating disc type granulator, which is used in Experimental Examples 5 to 8.
BEST MODE FOR CARRYING OUT THE INVENTION
A major feature of the preparation process of the present invention is to tumble a powder by using a specific granulator.
In this specification the tumbling means that polytetrafluoroethylene (PTFE) particles rotate and move around while being rubbed with each other or brought into contact to inner surfaces of the side plate of the granulator.
In FIG. 1, numeral 1 represents a granulator with a rotating inclined disc and a rotating side plate, which comprises the inclined disc 2, side plate 3, agitator 4 having agitator blades and wall scraper 6.
Examples of such a granulator are, for instance, Irich Reverse Flow Type High Speed Mixer Model R02 and R08W available from Nippon Irich Co., Ltd., and the like.
FIG. 1 is a cross-sectional and partly broken view for explaining a specific granulator
REFERENCES:
patent: 3345683 (1967-10-01), Eirich et al.
patent: 3674241 (1972-07-01), Eirich et al.
patent: 3882217 (1975-05-01), Banham et al.
patent: 4143110 (1979-03-01), Morozumi et al.
patent: 4611922 (1986-09-01), Eirich
Manfred H. Pahl, "Mischen beim Herstellen und Verarbeiten von Kunststoffen", 1986, pp. 166-167. (No translation).
Asano Michio
Kawachi Shoji
Shimizu Tetsuo
Tanigawa Shingo
Daikin Industries Ltd.
Merriam Andrew E. C.
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