FIELD OF INVENTION :
This invention relates to a process and apparatus for pyrolysis of thin coatings of polymer mixtures on conducting webs.
BACKGROUND OF INVENTION
Deleterious impact on battery efficiency, performance, cycling-life etc, of resistance at the interface of the conductive metal
and non-conductive battery elements is a natural phenomenon known in the art. To reduce this interfacial resistance is all the more
crucial in high energy-density in high energy-density batteries.
US Patent No.5840371 describes a process for reduction of interfacial resistance at the anode, wherein a thin coating of mixtures of poly-functional organic compounds, mono-polymers and copolymers is applied to the copper current collector web, followed by short-duration pyrolysis at high temeprature in non-oxidizing atmosphere and subsequent quenching also in non-oxidizing atmosphere. In the direct transition of organic compounds/po1ymers/co-po1ymers from the solid phase to gaseous phase in pyrolysis, cracking of these constituents takes places. Gaseous bye-products with harmful impact on interfacial resistance are allowed to escape, while beneficial bye-products transition into a thin g1azing-1ayer solidifies and gets firmly anchored to the copper web during subsequent quenching. Coating compounds are so selected that in addition to reduction of inter-

facial resistance, final layer also improves its capability of withstanding the highly corrosive chemical action of the battery electrolytes in repeated cycling to meet another important performance criterion of modern batteries. Coating layers are extremely thin (of the order of 0.1 - 0.3 gms per square foot) and pyrolysing process controlled for both temperature and time.
OBJECTS OF THE INVENTION
An object of this invention is to propose a continuous process and apparatus for pyrolysis of thin coatings of polymer mixtures on conducting webs.
Another object of this invention is to propose a continuous process and apparatus for pyrolysis of thin coatings of polymer mixtures on conducting webs which ensures a firm bond and quality of uniform thickness of the bye-product layer of pyrolysis process on long lengths of the web.
Yet another object of this invention is to propose a continuous process and apparatus for pyrolysis of thin coatings of polymer mixtures on conducting webs which is continuous.
Still another object of this invention is to propose a continuous process and apparatus for pyrolysis of thin coatings of polymer mixtures on conducting webs which is efficient.
DESCRIPTION OF INVENTION
According to this invention there is provided a process for pyrolysis of thin coatings of polymer mixtures on conducting webs which comprises in subjecting the webs to the step of pyrolysis followed by quenching in an inert atmosphere and while the web is in movement at a uniform speed and that the web at least during the step of pyrolysis is in a suspended state.
Further, according to this invention there is provided an apparatus for pyrolysis of thin coatings of polymer mixtures on conducting webs comprising:
i) a chamber;
ii) a pair of plates disposed in a spaced relationship to each other and such as to define a traverse space therebetween for the traverse of the web; iii) at least one of the plates being heated so as to define
a pyrolysis zone; iv) an inlet guide plate with said chamber and carried on
hinges in the end proximal to said chambers;
v) an outlet guide plate with said chamber and carried on hinges in the end proximal to said chamber and such as to define a quenching zone;
vi) an inlet for introduction of inert gas in said pyrolysis and quenching zone.
In accordance with this invention, the chamber IB formed by an upper and lower hood disposed in a spaced relationship to each other, said spaced plates provided within said chamber. Either one or both of said plates are connected to any suitable heating means. Alternatively, one of the plates is connected to a heating means, the other plate being a simple reflector.
The chamber has a first partition wall such as to define an inlet zone, a second partition all spaced from the first partition wall such as to define a pyrolysis zone and a third partition spaced from said second partition such as to define a quenching zone. The plates are disposed in the pyrolysis zone.
Further, in accordance with this invention, the inlet and outlet guide plates each comprise convexly curved plates in the vertical plane. The colder ends of the plates are freely supported on
roi1ers.
DESCRIPTION WITH REFERENCE TO DRAWINGS
Further objects and advantages of this invention will be more apparent from the ensuing description when read in conjunction with the accompanying drawings and wherein:
Fig.l shows the apparatus of the present invention.
Thin current collector web 1 is heated to the desired pyrolysing temperature as it is pulled at a uniform linear speed through a tunnel between two plates 2 and 3 heated externally by heating arrangements 5 and 6, said tunnel being located in a gap between two convexly curved stainless steel plates 7 and 8 over which the web slides in contact at its entry into and exit from the tunnel, said curved plates and tunnel being so located that the web does not come into contact with any tunnel wall as it moves through it. The two convex1y-curved plates are carried on hinges 9 and 10 at the ends nearer the heated tunnel, while their other colder ends are freely supported on rollers 11 and 12, said arrangement permitting free heat-expansion of plates.
Non-oxidising atmosphere for the pyrolisation and quenching processes is provided by encasing the entire tunnel-section and segments of the convexly curved plates by upper and lower hoods 13 and 14, creating the desired inert atmosphere in the chamber so made and maintaining continuous inflow to compensate for leakages. Web enters and exits hood 13 through slits 15 and 16 at its two ends. Hood 13 is further split by partitions 17 and 18 into zones 19, 20 and 21 meant for entry, pyrolisation and quenching of web respectively. Inert gas flows into the quenching zone through pipe 22 and exits into the pyrolysing zone, where additional inert gas is also introduced through elliptic pipe 23
with suitable holes which direct gas-flow in laminar fashion in direction shown by arrow 24. Gaseous bye-products of pyrolising process flow through slit in partition 17 to entry chamber 19 and flow thereafter through pipe 25 and neutralizing bath 26 for removal of toxic components before discharge into the atmosphere.

WE CLAIM:
1. A process for pyrolysis of thin coatings of polymer
mixtures on conducting webs which comprises in subjecting the
webs to the step of pyrolysis followed by quenching in an inert
atmosphere and while the web is in movement at a uniform speed
and that the web at least during the step of pyrolysis is in a
suspended state.
2. A process as claimed in claim 1 wherein the web slides
over a convexly curved plate provided at the inlet and outlet end
of a pyrolysis zone.
3. An apparatus for pyrolysis of thin coatings of polymer
mixtures on conducting webs comprising:
i) a chamber;
ii) a pair of plates disposed in a spaced relationship to each other and such as to define a traverse space therebetween for the traverse of the web; iii) at least one of the plates being heated so as to define
a pyrolysis zone; iv) an inlet guide plate with said chamber and carried on
hinges in the end proximal to said chamber;
v) an outlet guide plate with said chamber and carried on hinges in the end proximal to said chamber and such as to define a quenching zone;

vi) an inlet for introduction of inert gas in said pyrolysis and quenching zone.
4. An apparatus as claimed in claim 3, wherein said
chamber has an upper and lower hood disposed in a spaced
relationship to each other, said spaced plates are provided
within said chamber.
5. An apparatus as claimed in claim 3, wherein either one
or both of said plates are connected to any suitable heating
means.
6. An apparatus as claimed in claim 3 wherein one of the
plates is connected to a heating means, the other plate being a
simple reflector.
7. An apparatus as claimed in claim 3, wherein chamber has
a first partition wall such as to define an inlet zone, a second
partition wall spaced from the first partition wall such as to
define a pyrolysis zone, and a third partition spaced from said
second partition such as to define a quenching zone.
8. An apparatus as claimed in claims 4 and 7, wherein
plates are disposed in the pyrolysis zone.

9. An apparatus as claimed in claim 8 wherein the inlet and outlet guide plates each comprise convexly cureved plates in the vertical plane. The colder ends of the plates are freely supported on rollers.