Plastic and nonmetallic article shaping or treating: processes – With severing – removing material from preform mechanically,... – To form particulate product
Patent
1994-11-15
1997-05-06
Vargot, Mathieu D.
Plastic and nonmetallic article shaping or treating: processes
With severing, removing material from preform mechanically,...
To form particulate product
26421123, 264349, 366 81, 366 85, 425204, 425205, 425208, 425308, B29C 4750, B29C 4764
Patent
active
056268068
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to the incorporation of carbon black, usually together with other fillers, in a polymeric material such as natural and synthetic rubber as part of the procedure of compounding.
2. Description of the Related Art
As has been known for many years, natural or synthetic rubber must be subjected to intensive working to make it softer and more pliable prior to vulcanisation. It has also been known for many years that to improve its characteristics, especially its tensile strength, and make it suitable for the manufacture of articles such as pneumatic tires, fillers must be incorporated and dispersed in the mix, the principal filler in terms of the proportion by weight utilised and the most important in terms of its effect on the characteristics of the compound being carbon black.
As manufactured particulate carbon black takes the form of groups of fused particles known as "primary aggregate". The groups are also more loosely interconnected in chains referred to as the "structure" of the filler. Successful incorporation requires that as high a proportion as possible of the voids existing between the particles of a group become filled with polymer and successful blending requires that the chains are at least to some extent broken up so as to achieve as even a dispersion as possible of the groups, or broken chains, within the body of polymer. At the same time the treatment should not be such as to destroy a high proportion of the groupings of particles, because the fusion or welds between these are believed to provide the necessary reinforcement of the compound.
Hitherto the processes of filler incorporation, blending and homogenising, and mixing or masticating have been carried out simultaneously by subjecting the heterogeneous mixture of polymer particles, carbon black and any other desired fillers to intensive working e.g. by passing it between opposed, counter-rotating rollers of a mill or by forcing it through specially shaped screws. The intensive working of the mixture generates considerable heat--typically in excess of 170 degrees centigrade--sufficient to plasticise the polymer. The perceived solution to poor incorporation or dispersion is to repeat the mixing process, the same batch of mixture being objected repeatedly to intensive working, or to extend the mixing screw so that the mixture is subjected to a lengthier mixing procedure. This of course leads to high energy consumption.
SUMMARY OF THE INVENTION
The present invention proceeds from the realisation that to plasticise the polymer is counter-productive to the aims of filler incorporation and uniform filler dispersion. According to the present invention the steps of filler incorporation and dispersion are separated from subsequent treatments of the mixture such as blending, milling or calendaring and are carried out at much lower temperatures. Consequently at least at the stage of incorporation the polymer particles remain relatively hard and their hardness is utilised in the incorporation process by causing a smearing action between the polymer particles and the filler primary aggregate. The closer the polymer particles are to their plasticising temperature the less the phenomenon of smearing will occur. This is believed to be the reason why existing mixing procedures are relatively inefficient in achieving adequate incorporation and dispersion of fillers, and why merely to repeat or to extend the mixing procedure is far from the optimum solution as well as being wasteful of energy.
A further significant benefit of carrying out incorporation of the carbon black and other fillers at temperatures well below the plasticising temperature of the polymer is both the avoidance of degradation or scorching of the polymer which can occur in conventional processes and especially avoidance of the shrinkage which occurs when a high temperature polymer preform or article is cooled. This phenomenon of shrinkage makes high quality control in conventional processes extremely difficult
REFERENCES:
patent: 2319859 (1943-05-01), Hale
patent: 4917834 (1990-04-01), Hadermann et al.
patent: 5000900 (1991-03-01), Baumgartner
patent: 5129729 (1992-07-01), Geyer
patent: 5267788 (1993-12-01), Rockstedt
patent: 5320796 (1994-06-01), Harashima et al.
patent: 5348388 (1994-09-01), Geyer
Holroyd Colin
Holroyd Eric
Holroyd Associates Limited
Vargot Mathieu D.
LandOfFree
Carbon black incorporation in polymeric material does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Carbon black incorporation in polymeric material, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Carbon black incorporation in polymeric material will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2130268