Title of Invention

AN APPARATUS FOR INTRODUCING AN ADDITIVE ONTO A POLYOLEFIN POWDER

Abstract The invention provides an apparatus for introducing additives onto a polymer powder. It also provides a method' for introducing an additive into a polyolefin powder, which method comprises the following steps: (a) adding the additive in a solvent to form a solution; and (b) introducing the solution to the polymer powder at a temperature of 60°C or more, wherein, the solution is introduced to the polymer powder by spraying via a heated spraying means.
Full Text The present invention concerns an improved method for introducing additives into a
polymer powder or fluff, and in particular into polyethylene powder. The method is
advantageous, since it is capable of introducing the additives in a homogeneous
manner throughout the polymer powder without the need for processing the powder
through an extruder. The invention also covers the device that was used to
implement said method.
For many years it has been known to introduce additives into polymers, such as
polyethylene and polypropylene, in order to improve the properties of the polymers.
Additives may impart many different advantageous effects to the polymers. Typical
additives include additives for protection against UV radiation, anti-corrosion
additives, and anti-oxidant additives. Generally the simplest method for introducing
these additives into the polymers has been to extrude the polymer in the presence of
the additives. The extrusion process causes melting of the polymer, and as the
molten or softened polymer is extruded through a die, the additives become evenly
mixed through the polymer volume, leading to generally homogeneous distribution of
the additives throughout the extruded pelletised product.
Although the majority of polyethylene and polypropylene, and other similar polymers,
sold on the market is delivered in an extruded pellet form, this is not appropriate for
all applications. For some applications, a powder or fluff form of product is
preferable, for example in the case of high molecular weight resins which are difficult
to extrude, or where extrusion would cause degradation. Due to the nature of the
manufacturing process, polymers are typically obtained in powder form from a
reactor. It is this powder that is introduced into an extruder with the required
additives. However, if the powder is to be sold unextruded, the problem arises of
how to introduce the required additives without an extrusion procedure.
In the past, attempts have been made to solve this problem by blending the powder
with the additives in solid form, or by dissolving the additives in a solvent such as a

C12 fraction, at around 40°C, and then adding the solution to the powder. These
attempts have met with limited success. Blending the additives with the powder in
solid form does not allow sufficiently homogeneous incorporation of the additives.
Employing a solvent may improve homogeneity. However, many additives are not
soluble in appropriate solvents and cannot be introduced in this manner. Increasing
the temperature of the solvent has not been thought to be a solution to this problem
in the past, since sparingly soluble additives would tend to precipitate out of solution
at cold spots in the system, causing blockages. This in turn would lead to process
shutdown, rendering the process economically non-viable.
It is an aim of the present Invention to solve the problems associated with known
methods, as discussed above. Thus, the present invention seeks to provide an
improved method and apparatus for introducing additives into a polymer powder or
fluff, and in particular into polyethylene or polypropylene powder.
Accordingly, the present invention provides a method for introducing an additive onto
a polyolefin powder, which method comprises the following steps:
(a) adding the one or more additive(s) in a solvent;
(b) heating mixture (a) to a temperature of at1'least 60 °C in order to
completely dissolve the one or more additive(s);
(b) introducing the heated solution (b) onto the polymer powder
wherein, the solution is introduced onto the polymer powder by spraying via a heated
spraying means.
In the context of the present invention, powder means any form of the polymer that is
in a particulate form and has not been extruded. The particles of polymer may be of
any size normally produced in an industrial manufacturing process. Typically the
particles are produced by sedimentation into a settling leg of a polymerisation
reactor. These particles are often termed fluff. Generally such fluff particles range in
size and are 1600 µm or less in diameter. Preferably they are 1500 µm or less in
diameter, and more preferably from 10 µm to 1000 µm in diameter. Most preferably
the particles range from 100-1000 µm in diameter. The mean particle diameter for
monomodal polymer is preferably 300 µm or greater, whilst for bimodal polymer it is
preferably 125 µm or greater. Typical powder particle size distributions for
monomodal and bimodal polymers respectively are provided In Table 1 and Table 2.
Table 1 - Typical powder particle size distribution for a monomodal polyethylene
Table 2 - Typical powder particle size distribution for a bimodal polyethylene
The characteristic properties of the polymer are not especially limited, but generally it
is a high density polymer. Preferably the polymer has a specific gravity of from
920-970 kgrrr3 in the case of a monomodal polymer, and from 920-965 kgrrr3 in the
case of a bimodal polymer. Preferably the polymer has a bulk density of from
380-520 kgrrr3 in the case of a monomodal polymer, and from 280-470 kgrrr3 in the
case of a bimodal polymer. The melt index of the polymer is not especially limited,
but preferably in the case of a monomodal polymer, the melt index (2.16 kg at
190°C) ranges from 0.05-2.0 g/10 mins, and in the case of a bimodal polymer from
0.03-60.0 g/10 mins. In the case of a monomodal or bimodal polymer, it is preferred
that the specific heat capacity ranges from 0.40 kcal/kg°C at 20°C to 0.55 kca!/kg°C
at100°C.
This invention is particularly suited to powder having these characteristics, especially
polyethylene powder having the above characteristics.
The method of the present invention is particularly advantageous, since it allows
larger quantities and varieties of additives to be introduced into polymer powders,
without the need to extrude the powder. Blockage of the system, which is known to
be a difficult problem for high temperature processes where the solvent is likely to be
subject to large temperature fluctuations at some points in the system, may be
avoided by maintaining circulation of the solution in the system at a sufficiently high
flow rate to impede precipitation of the additives. In particular, blockage is also
avoided by heating the spraying means, which would otherwise be a likely point for
precipitation and blockage to occur.
The present invention will now be described in more detail by way of example only,
by reference to the followinr^Figures, in which:
Figure 1 shows an exemplary apparatus of the present invention, detailing the
vessels fo'r dissolving the additives, the parallel pumps and filters, the nozzle for
spraying and the long communication loop for maintaining circulation of the additive
solution; and
Figure 2 shows a cross-section of a heated nozzle for spraying the additives onto the
polymer product - hot fluid is directed around a central portion through which the
additive solution is fed to the nozzle mouth for spraying.
To put the present method in context, a typical process for producing the polymer
powder will first be described. Such a process generally employs a turbulent flow
reactor such as a continuous pipe reactor in the form of a loop. However, other
types of reactors such as stirred reactors may be used.

Polymerisation is carried out in a loop reactor in a circulating turbulent flow. A so-
called loop reactor is well known and is described in the Encyclopaedia of Chemical
Technology, 3rd edition, vol.16 page 390. This can produce LLDPE (linear low
density polyethylene) and HDPE (high density polyethylene) resins in the same type
of equipment. A loop reactor may be connected in parallel or in series to one or
more further reactors, such as another loop reactor. A loop reactor that is connected
in series or in parallel to another loop reactor may be referred to as a "double loop"
reactor.
In the double loop reactor according to the present invention, the process is a
continuous process. A monomer (e.g. ethylene) polymerises in a liquid diluent (e.g.
isobutene) in the presence of a comonomer (e.g. hexene), hydrogen, catalyst, and
activating agent. The slurry is maintained in circulation by an axial pump consisting
in a reactor essentially of vertical jacketed pipe sections connected by trough
elbows. The polymerisation heat is extracted by a water cooling jacket. The reactor
line includes two double loop reactors that can be used in parallel or in series. The
approximate volume of the reactors may be about 100m3. Monomodal grades are
produced with the parallel or series configuration and bimodal grades are produced
with the series configuration. *
The product (e.g. polyethylene) is taken out of the reactor with some diluent through
settling legs and discontinuous discharge valves. A small fraction of the total
circulating flow is withdrawn. It is moved to a polymer degassing section in which the
solid content is increased.
While being depressurised, the slurry is transferred through heated flash lines to a
flash tank. In the flash tank, the product and diluent are separated. The degassing is
completed in a purge column. A conveyor drying unit may be employed before the
purge column in some instances
The powder product transported under nitrogen to fluff silos may remain as fluff and
be additivised in accordance with the present invention, or may be extruded into
pellets along with some specific additives. A pellet treatment unit comprising silos
and hot and cool air flows allows the removal of residual components from the
pellets. The pellets then are directed to homogenisation silos before final storage.
The gas exiting the flash tank and the purge column is treated in a distillation
section. This allows the separate recovery of diluent, monomer and comonomer.
This embodiment of the double loop reactor process is usable with chromium type,
Ziegler-Natta type or metallocene type catalysts. Each catalyst type may have a
specific injection system.
it will be seen from the above that the present invention relates to the additivation of
the polymer at the end of the exemplary production process.
In the present invention, it is preferred that the temperature of the solution is at 60°C
or higher when added to the polymer powder. Typically the temperature may be in
the range of from 60°C up to the flashpoint of the solvent being employed, for safety
reasons. More preferably the temperature may be from 60-160°C, or 100-120°C.
Typically the process is carried out at around 110°C in most cases.
The solvent employed is not especially limited, provided that it does not adversely
affect the polymer product. Typically the solvent comprises a hydrocarbon fraction
Cn, wherein n is an integer of 4-24. More preferably n is an integer of from 6-18 and
most preferably an integer of from 8-14. Typically the solvent employed is a C12
fraction, but dodecane or isododecane may be added to the fraction if desired.
Similarly other solvents may be added to the other preferred solvent fractions, if
desired.
The additive employed is not especially limited, and may comprise any additive
useful for improving the properties of the polymer. Generally the additive comprises
one or more of an anti-oxidant, an anti-corrosive agent and a UV protective agent.
Typically, antioxidant additives include BHT, DLTDP and Irganox 1076. Preferably,
the anti-UV additive includes Chimasorb 944 LD.
In a preferred embodiment, the method is carried out using a nozzle as a spraying
means. The nozzle is not especially limited provided that it can withstand the
solution and the heating involved in the method. Typically the spraying means is
heated to a temperature at or above the temperature of the solution, although in
some embodiments the spraying means may be heated to a lower temperature,
depending on the solubility of the additives in the solvent employed.
The method of the present invention may be applied to any polymer powder, but
typically polyolefin powders are preferred. In the most preferred embodiments the
polymer powder is selected from polyethylene powder and polypropylene powder,
with polyethylene powder being the most preferred.
In a process for producing polyolefins, a conveyor is often employed for drying the
polymer powder after it has been removed from a reaction vessel. Often a purge
column is employed after the conveyor dryer to complete the drying process. In
some embodiments, the solution may be introduced'to the polymer powder by
spraying onto the powder on the conveyor. Alternatively the solution may be sprayed
into a mixer on the powder if desired. In preferred embodiments, the method
includes a further step of removing the solvent from the polymer powder after
spraying, preferably using a purge column.
The present invention also provides an apparatus for introducing an additive into a
polyolefin powder, which apparatus comprises the following elements:
(a) a dissolution vessel for dissolving the additive in a solvent to form a
solution;
(b) a heated spraying means for introducing the solution to the polymer
powder; and
(c) a communicating section connecting the dissolution vessel to the
heated spraying means;

wherein, between the dissolution vessel and the spraying means are situated at least
two filters in parallel formation for removing solids from the communicating section,
and at least two pumps in parallel formation for pumping the solution through the
communicating section to the heated spraying means.
In the apparatus of the invention, the parallel formation of the filters and the pumps
allows one of each to be removed from the system for servicing without the
requirement for shutting down the production process. This is important in the
present process, since precipitation of the additives can occur and block the system
if it is not properly maintained. Furthermore, maintaining circulation in both pumps
and both filters, except when in maintenance, prevents precipitation in these
components and reduces the requirement for servicing.
Preferably, the communicating section comprises a loop extending from an exit port
in the dissolution vessel to an entry port In the dissolution vessel, and the heated
spraying means is connected to the loop via a further communication section
downstream from the filters and the pumps, via a three-way valve. The purpose of
the loop is to allow circulation of the solution around the system at all times, even
when spraying ceases. Typically, the flow rate of the solution through the
communication section is maintained at a rate sufficiently high to prevent
precipitation of the additive in the communication section, which may occur due to
temperature reduction. When the flow rate of the solution through the
communication section is maintained at a high rate the further communication
section preferably comprises a control valve to reduce the flow rate of the solution
into the heated spraying means. This ensures that the pressure of the solution at the
point of spraying is not too high. The communication section, and the further
communication section, preferably comprise flow meters for monitoring the flow rate
in each section. It is further preferred that there is a pressure meter in the
communication section to monitor the pressure in that section. This is to ensure that
the pressure is sufficient for proper functioning of the control valve in the further
communication section. Typically the further communication section is very much

shorter than the communication section. This is to allow easier maintenance of this
section, should any blockage occur.
In a preferred embodiment a mixing vessel may be employed in place of the
dissolution vessel. The mixing vessel receives the return from the loop and has an
exit port for introducing the solution from the vessel into the communication section,
in the same way as the dissolution vessel. However, in this embodiment dissolution
takes place outside of the main section of the loop, avoiding the need to expose any
part of the communication section or the loop to solid additives or fresh solvent. In
this embodiment, the dissolution vessel is used to create the solution, which is then
fed into the mixing vessel.
If desired, fresh solvent may be introduced via a valve to any part of the system.
Preferably the apparatus is arranged such that fresh solvent may be added to the
line feeding the solution from the dissolution vessel to the mixing vessel.
It is also preferred that a membrane pump is employed to feed the solution from the
dissolution vessel to the mixing vessel. The parallel pumps are also preferably
membrane pumps. ¦*
The present invention will now be described in more detail by way of example only,
by reference to the following specific embodiments.
Examples
The operation of a typical device for additivising a polymer product according to the
present invention is outlined below.
Figure 1 shows a typical apparatus of the present invention for additivising polymer
fluff product. Additives are introduced into the dissolution vessel, along with solvent.
The solution is heated and stirred as necessary until all of the additives have
dissolved. The additive solution is taken from the dissolution vessel and pumped via

a membrane pump into the long loop communication section, which leads into the
mixing vessel. Solvent may also be added via this feed, if more solvent becomes
necessary. The additive solution is kept in circulation within the communication loop
at a sufficient flow rate to ensure that precipitation does not occur. The mixing
vessel also helps to ensure that any solids that might form are quickly dissolved
once again. The pressure meter and flow meter in the loop ensure that the required
flow is maintained. Parallel membrane pumps propel the fluid around the loop, whilst
parallel filters ensure that any solids are removed from the loop. These pumps and
filters can be serviced without switching the system off, since the parallel
arrangement allows one pump or filter to be serviced whilst the remaining one is still
operational. A further short communication section attaches the loop to the nozzle
via a three way valve. The additive solution is fed down this line from the loop and
through a control valve, which reduces the pressure at the nozzle to a level
appropriate for spraying. The additive solution is then sprayed directly onto the
polymer fluff.
The nozzle is heated to ensure that blockages do not occur. A nozzle adapted for
use with the present invention is depicted in Figure 2.
As discussed above, the additive is added as an additive composition in solution.
Examples of additive solutions that may be employed in the present invention
include the following:
1. BHT, 9wt.%; DLTDP, 13wt.%; Irganox 1076, 18wt.%; and
Isododecane solvent, 60 wt.%
2. Irganox 1076, 30 wt.%; Chimasorb 944 LD, 25 wt.%; and Isododecane
solvent, 45 wt%
All of these example additive compositions may be employed in the protocol
described above. The above solutions are particularly effective for additivising
polyethylene fluff and polypropylene fluff.
WE CLAIM :
1. An apparatus for introducing an additive onto a polyolefin powder, which apparatus
comprises:
(a) a dissolution vessel for dissolving the additive in a solvent to form a
solution;
(b) a heated spraying means for introducing the solution onto the polymer
powder; and
(c) a communicating section connecting the dissolution vessel to the heated
spraying means;
wherein, between the dissolution vessel and the spraying means are situated at least
two filters in parallel formation for removing solids from the communicating section, and
at least two pumps in parallel formation for pumping the solution through the
communicating section to the heated spraying means;
and wherein the communicating section comprises a loop extending from an exit
port in the dissolution vessel to an entry port in the dissolution vessel, and the heated
spraying means is connected to the loop via a further communication section
downstream from the filters and the pumps via a three-way valve.
2. The apparatus as claimed in claim 1, wherein the flow rate of the solution through
the communication section is maintained at a rate sufficiently high to prevent
precipitation of the additive in the communication section.
3. The apparatus as claimed in claim 2, wherein the further communication section
comprises a control valve to reduce the flow rate of the solution into the heated spraying
means.
4. A method for introducing an additive into a polyolefin powder using the apparatus
as claimed in any one of claims 1 to 3, which method comprises the following steps:
(a) adding one or more additive(s) to a solvent comprising a hydrocarbon fraction
C , wherein n is an integer of 4-24.;
(b) heating mixture (a) to a temperature of at least 60 °C in order to completely
dissolve the one or more additive(s);
(c) introducing the heated solution (b) onto the polymer powder,
wherein, the solution is introduced onto the polymer powder by spraying via a heated
spraying means.
5. The method as claimed in claim 4, wherein n is 12.
6. The method as claimed in claim 4 or claim 5 wherein the temperature employed
in step (b) is of from 100 to 120°C.
7. The method as claimed in any preceding claim, wherein the additive comprises
one or more of an anti-oxidant, an anti-corrosive agent and a UV protective
agent.
8. The method as claimed in any preceding claim, wherein the spraying means
comprises a nozzle.
9. The method as claimed in any preceding claim, wherein the spraying means is
heated to a temperature at or above the temperature of the solution.
10. The method as claimed in any preceding claim, wherein the polymer powder is
selected from polyethylene powder and polypropylene powder.
11. The method as claimed in any preceding claim, wherein the solution is
introduced to the polymer powder by spraying onto the powder in a mixer or onto
the powder in or after the purge column or onto the powder on a conveyor.
12. The method as claimed in any preceding claim, comprising the further step of
removing the solvent from the polymer powder after spraying.


The invention provides an apparatus for introducing additives onto a polymer powder. It also provides a method' for
introducing an additive into a polyolefin powder, which method comprises the following steps: (a) adding the additive in a solvent
to form a solution; and (b) introducing the solution to the polymer powder at a temperature of 60°C or more, wherein, the solution
is introduced to the polymer powder by spraying via a heated spraying means.

Documents:

01969-kolnp-2006 abstract.pdf

01969-kolnp-2006 assignment.pdf

01969-kolnp-2006 claims.pdf

01969-kolnp-2006 correspondence others.pdf

01969-kolnp-2006 description (complete).pdf

01969-kolnp-2006 drawings.pdf

01969-kolnp-2006 form-1.pdf

01969-kolnp-2006 form-3.pdf

01969-kolnp-2006 form-5.pdf

01969-kolnp-2006 international publication.pdf

01969-kolnp-2006 international search report.pdf

01969-kolnp-2006 pct form.pdf

01969-kolnp-2006 priority document.pdf

01969-kolnp-2006-assignment-1.1.pdf

01969-kolnp-2006-correspondence others-1.1.pdf

01969-kolnp-2006-form-13.pdf

01969-kolnp-2006-others document.pdf

1969-KOLNP-2006-(27-01-2012)-CORRESPONDENCE.pdf

1969-KOLNP-2006-(27-01-2012)-OTHER PATENT DOCUMENT.pdf

1969-KOLNP-2006-(27-01-2012)-PA.pdf

1969-KOLNP-2006-ABSTRACT 1.1.pdf

1969-KOLNP-2006-AMANDED CLAIMS.pdf

1969-KOLNP-2006-AMANDED PAGES OF SPECIFICATION.pdf

1969-kolnp-2006-assignment.pdf

1969-kolnp-2006-correspondence.pdf

1969-KOLNP-2006-DESCRIPTION (COMPLETE) 1.1.pdf

1969-KOLNP-2006-DRAWINGS 1.1.pdf

1969-KOLNP-2006-EXAMINATION REPORT REPLY RECIEVED.pdf

1969-kolnp-2006-examination report.pdf

1969-KOLNP-2006-FORM 1-1.1.pdf

1969-KOLNP-2006-FORM 13-1.1.pdf

1969-kolnp-2006-form 13-1.2.pdf

1969-kolnp-2006-form 18-1.1.pdf

1969-kolnp-2006-form 18.pdf

1969-KOLNP-2006-FORM 2.pdf

1969-KOLNP-2006-FORM 3-1.1.pdf

1969-kolnp-2006-form 3-1.2.pdf

1969-kolnp-2006-form 3.pdf

1969-kolnp-2006-form 5.pdf

1969-KOLNP-2006-FORM-27.pdf

1969-kolnp-2006-gpa.pdf

1969-kolnp-2006-granted-abstract.pdf

1969-kolnp-2006-granted-claims.pdf

1969-kolnp-2006-granted-description (complete).pdf

1969-kolnp-2006-granted-drawings.pdf

1969-kolnp-2006-granted-form 1.pdf

1969-kolnp-2006-granted-form 2.pdf

1969-kolnp-2006-granted-specification.pdf

1969-kolnp-2006-other patent document.pdf

1969-KOLNP-2006-OTHERS.pdf

1969-KOLNP-2006-PETITION UNDER RULE 137.pdf

1969-kolnp-2006-reply to examination report.pdf


Patent Number 248484
Indian Patent Application Number 1969/KOLNP/2006
PG Journal Number 29/2011
Publication Date 22-Jul-2011
Grant Date 19-Jul-2011
Date of Filing 13-Jul-2006
Name of Patentee TOTAL PETROCHEMICALS RESEARCH FELUY
Applicant Address ZONE INDUSTRIELLE C, B-7181 SENEFFE (FELUY)BELGIUM
Inventors:
# Inventor's Name Inventor's Address
1 FOUARGE LOUIS SLEUTELPASSTRAAT, 4, B-1700 DILBEEK BELGIUM
2 SILLIS MARJAN GERARD VAN LAETHEMLAAN 15, B-2650 EDEGEM, BELGIUM
3 D'HOOGHE LEO EGGENLAAN 11, B-2950, KAPELLEN BELGIUM
PCT International Classification Number C08J 3/20
PCT International Application Number PCT/EP2005/050561
PCT International Filing date 2005-02-09
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 04100591.9 2004-02-13 EUROPEAN UNION