U.S. patent application number 16/921142 was filed with the patent office on 2020-10-22 for equipment and process for producing polymer pellets.
This patent application is currently assigned to Borealis Technology OY. The applicant listed for this patent is Borealis Technology OY. Invention is credited to Mats Goransson, Richard Handwerk, Sune Larsson, Annika Smedberg, James Stadelman.
Application Number | 20200331167 16/921142 |
Document ID | / |
Family ID | 1000004939559 |
Filed Date | 2020-10-22 |
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United States Patent
Application |
20200331167 |
Kind Code |
A1 |
Goransson; Mats ; et
al. |
October 22, 2020 |
EQUIPMENT AND PROCESS FOR PRODUCING POLYMER PELLETS
Abstract
The present invention relates to an equipment and method for
producing polymer pellets which comprise one or more polymer
components and one or more further components, wherein in said
process at least one of said one or more further components is
incorporated into pellets by applying a liquid, which comprises
said at least one component, onto said pellets.
Inventors: |
Goransson; Mats; (Goteborg,
SE) ; Handwerk; Richard; (Schnecksville, PA) ;
Larsson; Sune; (Svanesund, SE) ; Smedberg;
Annika; (Myggenas, SE) ; Stadelman; James;
(Great Meadows, NJ) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Borealis Technology OY |
Porvoo |
|
FI |
|
|
Assignee: |
Borealis Technology OY
Porvoo
FI
|
Family ID: |
1000004939559 |
Appl. No.: |
16/921142 |
Filed: |
July 6, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14939557 |
Nov 12, 2015 |
10744678 |
|
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16921142 |
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12733377 |
Feb 25, 2010 |
9212240 |
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PCT/EP2008/060356 |
Aug 6, 2008 |
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14939557 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B01F 5/246 20130101;
Y10T 428/2938 20150115; B01F 5/0451 20130101; H01B 13/148 20130101;
B29B 9/16 20130101; B01F 11/0077 20130101; B29B 7/36 20130101; Y10T
428/2998 20150115; Y10T 428/2991 20150115; B01F 3/1242 20130101;
Y10T 428/2933 20150115; B29B 2009/161 20130101; Y10T 428/2982
20150115; B29B 7/945 20130101; C08F 110/02 20130101; B01F 5/0646
20130101; B01F 3/06 20130101; B29B 2009/163 20130101; B01F 11/008
20130101 |
International
Class: |
B29B 7/36 20060101
B29B007/36; B01F 11/00 20060101 B01F011/00; B01F 5/04 20060101
B01F005/04; B01F 5/06 20060101 B01F005/06; B01F 5/24 20060101
B01F005/24; B29B 7/94 20060101 B29B007/94; B29B 9/16 20060101
B29B009/16; H01B 13/14 20060101 H01B013/14; C08F 110/02 20060101
C08F110/02; B01F 3/06 20060101 B01F003/06; B01F 3/12 20060101
B01F003/12 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 27, 2007 |
EP |
07115032.0 |
Claims
1-44. (canceled)
45. An equipment for producing polymer pellets comprising one or
more polymer components and one or more further components, which
equipment comprises at least one first mixing apparatus for
introducing at least one of said further components onto polymer
pellets, which said first mixing apparatus comprises: an inlet for
feeding polymer pellets into said first mixing apparatus, to form a
pellet stream, a first mixing section provided with mixing means
for moving and mixing said pellet stream along said first mixing
section, at least one application device, said application device
applies said at least one further component(s) onto the polymer
pellets at one or more positions selected from prior to said first
mixing apparatus, at said inlet of said first mixing apparatus, and
within said section of said first mixing apparatus, and an outlet
for removing the mixed pellet stream from said first mixing
section, wherein said first mixing section is an elongated mixing
section having a longitudinal axis and is arranged substantially
horizontally within the longitudinal direction of the mixing
section to move the said pellet stream along said section from the
inlet towards the outlet, said mixing device for moving and mixing
said pellet stream in said first mixing section causes said mixing
section to at least vibrate and also oscillate and thereby to cause
the pellet stream to vibrate and oscillate within said mixing
section and said mixing device for moving and mixing said pellet
stream in said first mixing section is selected from the group
consisting of one or more of a vibration causing apparatus arranged
outside said first mixing section in an operational contact
therewith, oscillation causing apparatus arranged outside said
first mixing section in an operational contact therewith and
fluidization causing apparatus and wherein at least said vibration
causing apparatus is included from said group for non-gravimetrical
flow of said pellet stream in a substantially horizontal direction
in included from the stated group, no moving mixing device is
present within said first mixing section, and said at least one
application devices is arranged to extend at least partially within
the equipment for the pellet stream, to extend at least partially
within the polymer pellet stream and to be positioned to be at
least partly in contact with flowing polymer stream.
46. An equipment according to claim 45, wherein the first mixing
section of the first mixing apparatus of the invention has an
elongated structure comprising the inlet arranged at one end part
thereof and the outlet arranged at the other end part thereof.
47. The equipment according to claim 45, wherein said means for
moving and mixing said pellet stream in said first mixing section
is selected at least from the group consisting of one or more of
said vibration causing apparatus, oscillation causing apparatus or
a combination of said vibration causing apparatus and said
oscillation causing apparatus.
48. The equipment according to claim 45, wherein a longitudinal
axis at said inlet end of said first mixing section is defined to
be in a horizontal line (0.degree.), and said longitudinal axis at
said outlet end of said section is positioned 0 to 45.degree. above
or below from said horizontal line.
49. The equipment according to claim 45, which further comprises at
least one static mixing section arranged to follow the outlet of
said apparatus, allowing for further mixing of the pellet
stream.
50. The equipment according to claim 45, wherein said means for
moving and mixing said pellet stream in said first mixing section
is selected from the group consisting of one or more mechanical or
electromechanical vibrating causing apparatus and oscillating
causing apparatus.
51. The equipment according to claim 45 wherein said first mixing
section is arranged to cause the polymer pellet stream to flow and
said one or more further components to distribute among the pellets
through one or more of vibration, oscillation or fluidization, by
suspending the pellets in a fluidisation medium selected from
liquid or gas.
52. The equipment according to claim 45, wherein said first mixing
section has an elongated structure, which is, in its longitudinal
direction, connected at one end to said inlet of said apparatus and
at the other end to said outlet of said apparatus, whereby a
longitudinal axis of said first mixing section is along or inclined
from a horizontal line, and whereby, when said longitudinal axis at
said inlet end of said first mixing section is defined to be fixed
in said horizontal line, which is defined to be 0.degree., then
said longitudinal axis at said outlet end of said section is
inclined 0 to 3.degree. above or below from said horizontal
line.
53. The equipment according to claim 45, wherein said at least one
application device applies said further components in liquid medium
and is arranged within said first mixing section and comprises at
least one application unit which comprises at least one nozzle
comprising one or more injection holes through which the liquid is
supplied.
54. The equipment according to claim 45, wherein said apparatus
comprises at least one static mixing section, allowing for further
adsorption and mixing of the pellets, wherein said mixing section
comprises means for changing the flow direction of the pellets.
55. The equipment according to claim 45, wherein said mixing
section comprises one or more tubular bends for changing the flow
direction of the pellets each bend having a bending degree of at
least 20.degree., and wherein two adjacent bends are connected by
an intermediate part inclined downwards.
56. The equipment according to claim 55, wherein said bends are
arranged in a downward spiral manner causing the pellets to flow by
gravity through the bends.
57. The equipment according to claim 45, which is adapted to
operate in a continuous process for incorporating one or more
further components to pellets for producing polymer pellets
comprising one or more polymer components and one or more further
components.
58. The equipment according to claim 45, which is arranged in
separate pellet production process for producing said pellets for
temporary storage or for further use, or which is arranged in a
production line of an end product which is produced using said
pellets.
59. The equipment according to claim 45 for producing polymer
pellets wherein said at least one of said further components is
comprised in a liquid, said at least one first mixing apparatus for
introducing at least one of said further components onto polymer
pellets is at least one mixing apparatus for introducing said
liquid onto polymer pellets; and said at least one application
device for applying said at least one further components onto the
polymer pellets at one or more positions is selected from prior to
said apparatus, at said inlet of said apparatus, and/or within said
section of said apparatus is at least one application device for
applying said liquid onto the polymer pellets at one or more
positions selected from prior to said apparatus, at said inlet od
said apparatus and within said section of said apparatus and
combinations thereof.
Description
FIELD OF THE INVENTION
[0001] The invention is directed to an equipment for producing
polymer pellets, to a process for producing polymer pellets, to
polymer pellets as such and to articles produced using said polymer
pellets.
BACKGROUND OF THE INVENTION
[0002] The polymers are commonly in a form of pellets, granules and
powder, herein referred shortly as pellets, when used for producing
articles for a wide variety of end applications of polymers. Such
pellets contain one or more polymer compositions and one or more
further components, e.g. additives. Such further components may
typically be incorporated i.a for protecting or for modifying the
structure, property and/or function of 1) a pellet as such, which
pellet can be an intermediate pellet product that is processed to
further pellets or a final pellet for end use, or 2) a product
produced using said pellets, which product can be an intermediate
product which is further processed, e.g. crosslinked, to a final
product or a final product, such as a cable layer or pipe.
[0003] Said further components can be incorporated into the pellet
by adding component(s) to the polymer material before pelletising
the composition. In some applications, see e.g. WO0038895 of
Pirelli (=EP1150817) and EP1148518, one or more of said further
components may be added after pellet formation by depositing the
component(s) onto preformed pellet and allowing the component(s) to
be absorbed inside the pellet matrix.
[0004] To obtain a desired effect of the added further
component(s), it is important that said further component(s) is/are
distributed as uniformly, i.e. homogeneously, as needed throughout
a polymer pellet and also distributed uniformly between the
pellets. As an example, e.g. isotropy and homogeneity are
requirements in highly demanding field of electric cable
manufacturing.
[0005] Thus, the method for incorporating and distributing said one
or more further components within polymer pellets is very important
for the performance of an article produced from said pellets.
[0006] It is thus a challenge to add, i.e. distribute, such one or
more further components e.g. in a liquid medium onto the pellets.
During said distribution step said further component(s) present in
the liquid are typically allowed to impregnate into the pellets at
a temperature below the melting point of the major polymer
component of the polymer material of said pellet and then are
subjected to a drying step including a further equalisation, i.e.
homogenisation, step, if needed, for a predetermined time period in
order to allow said further component(s) to diffuse into the
pellets.
[0007] Mechanical mixing of the pellets e.g. during said
distribution step can lead to the generation of polymer dust. Since
the formed dust also absorbs said liquid, it may contribute to
premature reactions and/or provide a non-homogeneous performance of
the distributed further component(s). Thus, the dust must usually
be removed in a subsequent step, for example by screening and
elutriation. However, traces of dusty polymers often still remain
as residues which affect the performance of the resulting article,
such as an insulating layer.
[0008] As an example of said one or more further components that
are incorporated to pellets by distributing the component(s) onto
pellets, i.a. free radical generating agents can be mentioned. Free
radical generating agents are conventionally used for modifying a
polymer product via a radical reaction.
[0009] Free radical agents are used e.g. to initiate (a) a
crosslinking reaction in a polymer, i.a. primarily a formation of
interpolymer crosslinks (bridges) by radical reaction, (b) a
grafting reaction in a polymer, i.e. introduction of compounds to a
polymer chain (to backbone and/or side chains) by radical reaction,
and (c) a visbreaking reaction in a polymer, i.e. modification of
melt flow rate (MFR) of a polymer by radical reaction. These
polymer modifications are well known in the art.
[0010] When added to a polymer composition, free radical generating
agents act by generating radicals, typically by decomposing to
radicals, under conditions which enable the radical formation.
[0011] Crosslinking of polymers, e.g. polyolefins, substantially
contributes to an improved heat and deformation resistance, creep
properties, mechanical strength, chemical resistance and abrasion
resistance of a polymer. Crosslinked polymers, such as crosslinked
ethylene homo- and/or copolymers, are commonly used as a layer
material in wire and cable applications, such as insulating layer
material, semi-conducting layer material and/or jacketing layer
material. The crosslinked polymers are also widely used in other
end applications of polymers such as in pipe applications.
[0012] In wire and cable applications a typical cable comprises at
least one conductor surrounded by one or more layers of polymeric
materials. In power cables including medium voltage (MV), high
voltage (HV) and extra high voltage (EHV) said conductor is
surrounded by several layers including an inner semiconductive
layer, an insulation layer and an outer semiconductive layer, in
that order. The cables are commonly produced by extruding the
layers on a conductor. One or more of said layers are then
typically crosslinked for the above reasons.
[0013] Peroxides are commonly used free radical generating agents
used i.a. in the polymer industry for said polymer
modifications.
[0014] It is also known to crosslink polyolefins, such as
polyethylene, by introducing crosslinkable groups, such as
hydrolysable silane groups, into the polymer by copolymerisation or
grafting. The crosslinking of polymers with hydrolysable silane
groups is carried out by so-called moisture crosslinking (water
crosslinking) in the presence of e.g. a so-called silanol
condensation catalyst, for instance carboxylates of metals, such as
tin, zinc, iron, lead and cobalt; organic bases; inorganic acids;
and organic acids.
[0015] Further components such as additives may naturally also be
added onto pellets after pellet formation, such as antioxidants,
light stabilizers, UV stabilizers, crosslinking boosters, scorch
retardants, etc., as evident for a skilled person.
[0016] For example, it is important that a high voltage cable
including crosslinked HV cable, comprises an isotropic and
homogeneous insulating layer to obtain the high value of dielectric
strength required for its operation.
[0017] The above mentioned WO 0038895 describes a method for
introducing a liquid substance into polymer granules comprising
spraying the substance onto continuously flowing granules in a
static spraying chamber, passing the granules through a mixing
chamber comprising static mixing means without moving mechanical
elements to submit mixing thereof, and thereafter drying the
granules in a drying chamber.
[0018] The granules flow in a substantially continuous manner by
gravity through said spraying, mixing and drying chambers arranged
in substantial vertical alignment. The spraying chamber may
comprise a plurality of vertically arranged ducts. The static
mixing chamber is designed to deviate the granules flowing in the
central part of the mixing chamber towards the peripheral zone
thereof, and the granules flowing in the peripheral zone towards
the central zone thereof.
[0019] Known within the art is also the so-called continuous
zig-zag blender, for instance supplied by Patterson Kelly, wherein
a liquid substance is sprayed onto continuously flowing pellets.
The zig-zag blender comprises an entrance part in the form of a
drum section and thereafter a plurality of bends arranged in an
essentially horizontal spiral manner. The whole equipment rotates
360.degree. around its axis which results in movement of the
pellets and thus mixing. The zig-zag blender is not self-cleaning.
Moreover, the zig-zag blender comprises seals which are clear
contamination sources since a seal in a rotating equipment is
exposed to a continuous wear and therefore will be mechanically
damaged with time and thus have limited use life.
OBJECTS OF THE INVENTION
[0020] Thus, one object of the present invention is to provide a
simplified process and an equipment for introducing one or more
further components, preferably in a liquid medium, onto polymer
pellets for providing a homogeneous distribution of said further
component(s) among the pellets while protecting the physical
integrity of the pellets.
[0021] Preferably said equipment and process of the invention also
enables to decrease markedly or even prevent the formation of dust
due to mechanical abrasion.
[0022] Furthermore, the process and equipment of the invention
preferably allow a high distribution efficiency in terms of fast
distribution of said one or more further components onto pellets
and between the pellets. Preferably, at the same time
advantageously even distribution of said one or more components
inside a pellet and/or between the pellets is achieved with the
process and equipment of the invention.
[0023] The expression "distribution onto and between the pellets"
is equally referred herein as "distribution among(st) the
pellets".
[0024] Moreover, due to present invention high production rates of
polymer pellets with very feasible distribution efficiency of said
one or more further components by using a reduced size of equipment
may be obtained, if desired. The reduced size of the equipment of
the invention provides an industrially desirable solution.
Moreover, said equipment of invention, preferably with reduced size
compared to prior art solutions for said pellet production,
preferably has advantageous self-cleaning properties.
DESCRIPTION OF FIGURES
[0025] FIG. 1 is a flow chart of an equipment and method of the
invention.
DESCRIPTION OF THE INVENTION
[0026] The present invention is based on the finding that these
objectives can be achieved by a method and an equipment which
comprises a first mixing section (A) in which polymer pellets, onto
which one or more further component(s) are applied, are caused to
flow through vibration, oscillation and/or fluidisation.
[0027] Equipment
[0028] According to a first aspect, the present invention provides
an equipment for producing polymer pellets comprising one or more
polymer components and one or more further components, which
equipment comprises at least one first mixing apparatus (A) for
introducing at least one of said one or more further components
that are to be incorporated to said pellets, onto polymer pellets,
wherein said first mixing apparatus (A) comprises: [0029] an inlet
(1) for feeding polymer pellets into said first mixing apparatus
(A), [0030] a first mixing section (A) provided with mixing means
(2) for moving and mixing said fed pellet stream along said section
(A), [0031] at least one means (3) for applying said further
component(s) onto the fed polymer pellets at one or more positions
selected from prior to said apparatus (A), at said inlet (1) of
said apparatus (A) and/or within said section (A) of said apparatus
(A), and [0032] an outlet (4) for removing the mixed pellet stream
from said first mixing section (A), wherein said means (2) for
moving and mixing said pellet stream in said section (A) is
selected from one or more of a vibration means (2a), oscillation
means (2b) or fluidisation means (2c).
[0033] Preferably said at least one of said one or more further
components are introduced in a liquid medium, which is herein
shortly referred as "liquid", onto the pellets.
[0034] Thus a preferable equipment of the invention for producing
pellets comprising one or more polymer components and one or more
further components comprises at least one first mixing apparatus
(A) for introducing a liquid onto polymer pellets, wherein said
liquid comprises at least one of said further component(s) that are
to be incorporated into said pellets, said first mixing apparatus
(A) comprises: [0035] an inlet (1) for feeding pellets into said
first mixing apparatus (A), [0036] a first mixing section (A)
provided with mixing means (2) for moving and mixing said fed
pellet stream along said section (A), [0037] at least one means (3)
for applying said liquid onto said polymer pellets, prior to said
apparatus (A), at said inlet (1) of said apparatus (A) and/or
within said section (A) of said apparatus (A), and [0038] an outlet
(4) for removing the mixed pellet stream from said first mixing
section (A) characterised in that said means (2) for moving and
mixing said pellet stream in said section (A) is selected from one
or more of a vibration means (2a), oscillation means (2b) or
fluidisation means (2c).
[0039] The present invention is described below by referring to
preferable "liquid" as the medium for introducing said further
component(s). However, the invention is not limited to a liquid
medium, but, alternatively, it covers also embodiments wherein said
further component(s) can be introduced in solid powder form onto
the pellets.
[0040] The apparatus (A) of the invention is found to be
surprisingly effective for depositing the liquid homogenously onto
and between the pellets. The term "depositing" means herein
applying and distributing of liquid onto and between the
pellets.
[0041] The first mixing section (A) of the invention is for
transferring said pellet stream towards the outlet (4) of said
section (A) and simultaneously for mixing the pellets in order to
distribute and adsorb said one or more further components present
in said liquid onto a pellet, between the pellets and inside a
pellet. "Mixing" thus includes herein distributing the liquid and
the components thereof onto, between and inside the pellets.
[0042] As well known, "adsorption", "absorption", "distribution
inside a pellet", "impregnation" etc are used herein
interchangeably and mean the diffusion of the further component(s)
from the surface of the pellet inside the pellet matrix. The term
"Homogenisation" and "equalisation" include herein the above
diffusion in order to improve or complete the distribution between
and within the pellets.
[0043] The first mixing apparatus (A), mixing apparatus (A) and
apparatus (A) mean the same and are used herein interchangeably.
The equipment of the invention may comprise more than one of said
first mixing apparatus (A), preferably one. The first mixing
section (A), mixing section (A) and section (A) mean the same and
are used herein interchangeably. The mixing apparatus (A) may
comprise more than one first mixing sections (A), preferably one,
which section (A) is integrated with said inlet (1), said one or
more means (3) for applying at least one of the one or more further
components, outlet (4) and mixing means (2). The mixing section (A)
may comprise one or more inlet(s) (1) and outlet(s) (4), in any
position of section (A), for feeding and, respectively, removing of
pellets of the pellet stream.
[0044] The preferred first mixing section (A) of the first mixing
apparatus (A) of the invention has an elongated structure
comprising the inlet (1) at one of the two end parts thereof and
the outlet (4) at the other end part thereof.
[0045] It is also preferred that the elongated first mixing section
(A) is arranged horizontally or essentially horizontally. More
specifically the elongated first mixing section (A) is arranged
horizontally, whereby its longitudinal axis between inlet (1) and
outlet (4) is along the horizontal line (about 0.degree.), or
essentially horizontally, wherein the elongated first mixing
section (A) is declined so that the outlet (4) end deviates less
than 90.degree., preferably less than 45.degree., above or below
from said horizontal line. Accordingly, "horizontally" and
"essentially horizontally" means herein that said longitudinal axis
of the elongated first mixing section (A) at said inlet (1) is
defined to be in the horizontal line (0.degree.), and the
longitudinal axis at said outlet (4) end may be in the position
(declined) of 0 to 90.degree. above or below from said horizontal
line, preferably of from 0 to 45.degree., more preferably of up to
20.degree., more preferably of up to 15.degree., even more
preferably of up to 10.degree., above or below the horizontal line.
In this preferred arrangement said pellet stream proceeds
essentially horizontally along the longitudinal axis in said
section (A) from inlet (1) towards the outlet (4). The individual
pellets of within the moving pellet stream can move at the same
time in any directions.
[0046] It is furthermore preferred that said means (2) for moving
and mixing said pellet stream in said first mixing section (A) of
the mixing apparatus (A) of the invention is selected at least from
one or more of a vibration means (2a), oscillation means (2b) or a
combination of vibration and oscillation means (2a/2b).
[0047] It is known that vibration can be achieved e.g. by high
frequency and low amplitude. It is also known that oscillation
means a rotary movement. It is clear that the vibration and
oscillation is produced by an external source other than
fluidisation with gas or liquid medium. Fluidisation of the pellet
stream can be achieved by gas and/or liquid medium, e.g. as in
fluidised bed, but preferably the velocity of the liquid and/or gas
flow is less than the velocity of a conventional fluidised bed
mixer. It is evident that at least the vibrating and/or oscillating
movement of the pellet stream causes the individual pellets to move
in any directions within the moving stream.
[0048] The preferred first mixing section (A) of the mixing
apparatus (A) of the invention comprises at least vibration means
(2a) and/or oscillation means (2b) and is thus other than a
fluidised bed mixing system.
[0049] In the apparatus (A) according to the invention the pellets
are thus caused to flow through the first mixing section (A) by
vibration, oscillation or fluidisation, or in any combination
thereof. Thus the mixing means (2) of the invention may comprise
means which provide e.g. a combination of vibrating and oscillating
function. Preferably, said means (2) is a device which causes the
pellet stream to vibrate and oscillate at the same time.
[0050] In the apparatus (A) of the invention, when in operation,
the pellet stream flows at least non-gravimetrically due to mixing
means (2) of the invention. This offers the advantage that the
number of contacts between the pellets, in particular the surface
of the pellets, is increased and hence a more even and efficient
distribution between pellets and within pellets of the applied
liquid is obtained compared to an apparatus in which pellets are
caused to flow by gravity or by a rotational movement.
[0051] As used herein the term "non-gravimetrical flow" means that
another force than gravity is required in order to cause the
pellets to flow. In addition to said non-gravimetrical flow
provided by the apparatus (A) of the invention, it is naturally
possible to arrange the pellet stream to flow in said apparatus (A)
also gravimetrically for assisting the transfer and/or mixing of
the pellet stream.
[0052] Furthermore, the dimensions of the section (A) of said
apparatus (A) can be made rather small, e.g. smaller than for an
apparatus with gravimetrical flow. The small size of the apparatus
(A), in turn, also contributes to an enhanced contact between the
pellets and thereby a more efficient and more even distribution of
the liquid.
[0053] Still further, no mechanical mixing means including static
mixing means, such as baffles, or mechanically moving mixing means
are necessary inside the apparatus (A). Moreover, the apparatus (A)
according to the invention is more or less self-cleaning, for
instance, due to the continuous flow of pellets within the
apparatus. Alternatively, in addition to said mixing means (2) of
the invention, if desired, the apparatus can comprise additionally
also static and/or moving mixing means inside the first mixing
section (A).
[0054] The term "pellet stream" comprises said fed pellets and said
liquid applied to pellets. Furthermore, at least in case said means
(2) is a fluidisation means (2c), then the pellet stream comprises
additionally also a fluidisation medium for carrying said pellets
and liquid.
[0055] As used herein the term "polymer pellets" or shortly
"pellets" means any solid form of polymer material and includes
well known pellets, granules and small particles, such as polymer
powder, of polymeric material. "Pellet material" as used herein
naturally means said one or more polymer components and further
components that are present in a pellet of said fed pellets.
"Polymer material of pellets" means said one or more polymer
component(s) that are present in a pellet of said fed pellets. It
is evident, that said fed pellets may be the same, i.e. each pellet
comprise the same polymer component(s) and same further
component(s), or the fed pellets may be a mixture of two or more
type of pellets, whereby said two or more type of pellets have
differing polymer component(s) and/or further component(s).
[0056] The term "liquid" means a liquid medium which is to be
applied, deposited and distributed onto and between the pellets and
comprises, one or more further components, which are to be
incorporated to the pellets, optionally in a liquid carrier medium.
Such components are not limited and can be any components suitable
for incorporating to polymer pellets depending on the end use
application of the pellets. As non-limiting examples additives,
which term includes herein fillers, that are useful in polymer
applications can be mentioned. Said components may either be in
liquid form as such, so that they can be directly used in that
form. Alternatively, said to components may be solids which are
brought to liquid form by dissolution, dispersion, emulgation,
suspension or melting etc. The liquid in which solid further
components are contained may itself be one of said further
components or, alternatively, an inert solvent.
[0057] In one embodiment of the invention said equipment further
comprises at least one static mixing section (B) arranged to follow
the outlet (4) of the first mixing section (A), allowing for
further mixing of the pellets. Preferably, said section (B)
comprises a plurality of essentially vertically positioned bends
(5), for subjecting the pellets to flow continuously, suitably by
gravity, and to mix.
[0058] In another embodiment of the invention said equipment
further comprises at least one drying section (C) arranged to
follow said first mixing section (A), or to follow said optional
static mixing section (B), if present, for allowing further
absorption of said one or more further components present in said
liquid into the pellets.
[0059] Drying (C) section comprises one or more drying tanks
providing sufficient residence time for the component from said
liquid to be further absorbed from the surface to the inside of
said pellets.
[0060] The first mixing apparatus (A) of the invention can thus be
combined, if desired, with one or both of said static mixing
section (B) and said drying section (C). In one preferable
embodiment of the invention said equipment comprises said first
mixing apparatus (A), said static mixing section (B) and said
drying section (C), in that order.
[0061] It is evident for a skilled person that said equipment of
the invention may naturally comprise supporting means adapted to
support said means for applying the liquid onto the pellets, said
first mixing section (A), and, optionally, said static mixing
section (B), and, optionally, said drying section (C).
[0062] In one preferable embodiment of the equipment of the
invention at least one of said first mixing section (A), optional
static mixing section (B) and optional drying section (C) are avoid
of any mechanical mixing means, which are static and/or
mechanically moving, such as baffles, inside the said section.
Preferably in such embodiment said section (A), section (B), if
present, and section (C), if present, does not contain any
mechanical mixing means, more preferably, any static or
mechanically moving mixing means, inside the section.
[0063] The equipment of the invention may be operated in a batch
process or, preferably, in a continuous process for producing
polymer pellets by incorporating said one or more further
components into pellets. Preferably said equipment is adapted to
operate in a continuous process.
[0064] The term "continuous process" is a well known and widely
used term and means that the process is operated in a continuous,
essentially uninterrupted basis in a manner well known to a skilled
person.
[0065] Moreover, the equipment of the invention can be used in a
separately operating production process of said polymer pellets
which produced pellets are then supplied to end users, e.g. end
producers of articles prepared using said polymer pellets of the
invention.
[0066] Alternatively, said equipment can be arranged in a
production line of an end product which end product is produced
using said polymer pellets obtainable from the equipment of the
invention. In this arrangement said equipment naturally precedes
the end article forming unit.
Process of the Invention
[0067] According to a second aspect, the invention provides a
process for producing polymer pellets which comprise one or more
polymer components and said one or more further components, wherein
in said process at least one of said further component(s) is
incorporated into pellets by applying said at least one of said
further component(s) onto polymer pellets, and wherein said process
comprises the steps of: [0068] feeding the polymer pellets in a
first mixing section (A), which is preferably as defined above or
below, and arranged to cause the fed polymer pellets to flow and
mix through one or more of the following movements selected from
vibration, oscillation or fluidisation, [0069] applying at least
one of said further component(s) via at least one application means
(3), preferably as defined above or below, at one or more positions
selected from onto the fed polymer pellets prior to apparatus (A),
at said inlet (1) of said apparatus (A), which is preferably as
defined above or below, and/or within said first mixing section (A)
of said apparatus (A), which is preferably as defined above or
below, and recovering the obtained pellets in a conventional manner
as well known for a skilled person.
[0070] Preferably said at least one of said one or more further
components that are to be incorporated to pellets of the invention
are applied in a liquid as defined above or below.
[0071] Thus in a preferable embodiment, a process for producing
polymer pellets, which comprise one or more polymer components and
one or more further components, is provided, wherein in said
process at least one of said further component(s) is incorporated
into pellets by applying a liquid, which comprises said at least
one of said further component(s), onto said pellets and wherein
said process comprises the steps of: [0072] feeding polymer pellets
in a first mixing section (A), which is preferably as defined above
or below, and arranged to cause the fed polymer pellets to flow and
mix through one or more of the following movements selected from
vibration, oscillation or fluidisation, [0073] applying said liquid
via at least one application means (3), which are preferably as
defined above or below, onto the fed polymer pellets at one or more
positions selected from prior to said apparatus (A), at said inlet
(1) of said apparatus (A), which is preferably as defined above or
below, and/or within said first mixing section (A), which is
preferably as defined above or below, and [0074] optionally
subjecting the pellet stream leaving said first mixing section (A)
to a further mixing in a static mixing section (B), which is
preferably as defined above or below, and/or [0075] optionally
subjecting said polymer pellets obtained from said first mixing
section (A), or from said optional static mixing section (B), if
present, to a further drying in a drying section (C), which is
preferably as defined above or below, for a time period, and
recovering the obtained pellets in a conventional manner.
[0076] The recovery step is e.g. any conventional recovery of the
pellets for temporary storage and/or further use, as known for a
skilled person.
[0077] In said process at least one of said further components are
thus incorporated to said pellets by applying a liquid comprising
said at least one further component(s) onto said pellets in order
to allow said incorporation to occur. The term "incorporating"
means herein that the further component(s) are deposited and
distributed onto and between pellets and then absorbed inside the
pellets, i.e. within the pellet matrix.
[0078] It is also preferred that said fed pellet stream flows and
the pellets mix at least by vibrating and/or oscillating movement
along the longitudinal axis of the first mixing section from inlet
(1) towards an outlet (2) arranged at the other end in the
direction of the longitudinal axis of the mixing section (A).
[0079] Moreover, in the preferred process said pellet stream moves
horizontally or essentially horizontally along an elongated first
mixing section (A) from inlet (1) arranged at one end of said
elongated mixing section (A) towards the outlet (4) arranged at the
other end of said elongated mixing section (A), preferably said
pellet stream moves horizontally or essentially horizontally along
said longitudinal axis from said inlet (1) end of said first mixing
section (A), which is defined to be in said horizontal line
(0.degree.), towards said outlet (4) end of said mixing section
(A), which is positioned 0 to 90.degree. above or below from said
horizontal line, preferably between 0 to 45.degree., more
preferably up to 20.degree., suitably of up to 15.degree.,
preferably of up to 10.degree., above or below the horizontal
line.
[0080] In said process of the invention said vibration, oscillation
and/or fluidisation causes the one or more further components
present in the liquid to distribute evenly among the pellets and
within a shorter time period compared to prior art due to increased
contacts between the pellets in said pellet stream.
[0081] In a preferred embodiment of the process of the invention
the polymer pellets leaving the first mixing section (A) are passed
to a static mixing section (B), which preferably comprises a
plurality of essentially vertically positioned bends (5), wherein
the pellet stream flows, preferably continuously by gravity, for
further mixing said pellets and liquid in said pellets stream.
[0082] Furthermore, preferably the method comprises the step of
passing the mixed pellets through at least one drying section (C)
for allowing further absorption of the said further component(s)
present in said liquid into the pellets. In a preferable embodiment
of said drying section (C) the pellet stream flows preferably by
gravity through the drying section (C).
[0083] Moreover, the pellet stream can be heated prior to and/or
during the drying step (C).
[0084] The process of the invention is preferably carried out using
the equipment of the invention. The preferred equipment for
carrying out the process for producing pellets of the invention is
thus the equipment for producing pellets as defined above, below
and in claims.
[0085] Preferably the process of the invention operates in a
continuous basis, i.e. is a continuous process. The meaning of
continuous process is well known in the art. Alternatively, a
batch-process is also covered. Moreover, the process can be
operated as a separate polymer pellet manufacturing process or it
can be operated in a production line of an intermediate and/or end
product that is produced using polymer pellets obtainable by the
process of the invention.
[0086] The temperature during the first mixing step (A), during
said optional static mixing section (B), if present, and during
said optional drying section (C), if present, is not critical and
may vary and is typically above the solidification point of said
liquid and/or said added further component(s).
[0087] Further preferably, the operating temperature in each of
said section (A) and optional sections (B) and (C), may be selected
to be such that temperature of the polymer material of said fed
pellets is kept below the melting point of the major polymer
component of said fed pellet material, preferably at or above
ambient temperature. More preferably, the temperature of said fed
polymer pellets in said section (A) and, if present, in said
optional section (B) and/or optional section (C) is kept at least
10.degree. C., more preferably at least 15.degree. C., more
preferably at least 20.degree. C., below the melting point of the
major polymer component of the polymer material of said fed
pellets, as evident for a skilled person.
[0088] Residence time in each of said first mixing section (A),
optional static mixing section (B), if present, and drying section
(C), if present, can be varied depending on the desired degree of
distribution among and within the pellets. The desired degree of
distribution may vary i.a. depending on the one or more further
components, pellet material and the end use application of the
pellets, as well known to a skilled person.
DETAILED DESCRIPTION OF THE INVENTION
[0089] The features, preferable embodiments and variants of the
equipment and process of the invention are further described below.
It is understood that said features, embodiments and variants can
be combined in any combination and in any order.
[0090] Preferably, the first mixing section (A) of the apparatus
(A) of the invention an elongated structure with closed side
walls.
[0091] This structure of section (A) can have any suitable
cross-sectional shape, including round, e.g. circular,
cross-sectional shape and multiangular cross-sectional shape, e.g.
a rectangle or square. Alternatively, said structure may have a U-
or V-shape cross-section, in case open systems of section (A) are
desired.
[0092] Preferably, the first mixing section (A) of the apparatus
(A) of the invention comprises, preferably consists of, a
closed-wall, elongated structure, such as a tubular structure,
preferably a pipe, which is connected at one end in the
longitudinal direction of said section (A) to said inlet (1) of
said apparatus (A) and connected at the other end of said section
(A) to said outlet (4) of said apparatus (A) for receiving the fed
pellets and removing the mixed pellets; one or more application
means (3) for applying said liquid on the pellets; and mixing means
(2) for mixing and transferring the pellet stream.
[0093] Preferably, said section (A) is a pipe with a circular or a
rectangular or a quadratic cross-section shape. Alternatively, the
first mixing section (A) can be in the form of a closed tray, in
particular an essentially horizontally arranged tray.
[0094] In one preferred embodiment, said first mixing section (A)
has an elongated structure, preferably is a pipe as defined above,
which is, in its longitudinal direction, connected at one end to
said inlet (1) of said apparatus (A) and at the other end to said
outlet (4) of said apparatus (A). Preferably said longitudinal axis
of said section (A), such as pipe as defined above, is along
horizontal line, which is also known as central line, which is
defined to be 0.degree., or said longitudinal axis of said first
mixing section (A) may be declined 0.degree. to 90.degree. above or
below from said horizontal line. Preferably, when said longitudinal
axis at said inlet (1) end of said first mixing section (A) is
defined to be fixed in said horizontal line (0.degree.), then said
longitudinal axis at said outlet (4) end of said section (A) may be
inclined 0 to 90.degree. above or below from said horizontal line,
such as up to 20.degree., suitably of up to 15.degree., preferably
of up to 10.degree., above or below the horizontal line from the
horizontal line.
[0095] Preferably, when said longitudinal axis at said inlet (1)
end of said first mixing section (A) is defined to be fixed in said
horizontal line (0.degree.), then said longitudinal axis at said
outlet (4) end of said section (A) may be inclined 0 to 3.degree.
above or below from said horizontal line
[0096] Preferably, the first mixing section (A) itself does not
rotate 360.degree. around its axis that is parallel to the flow
direction of the pellet stream. If means (2a) and (2b) are used,
then vibration and oscillation of the pellet stream is caused by
means (2) which is preferable arranged outside section (A) in
operational contact therewith in a manner known to a skilled
person. Thus in case of means (2a) or (2b), the mixing section (A)
can be moved by means (2a) and/or (2b). However such movement of
section (A) preferably excludes the rotation of section (A) of full
360.degree. around the axis that is parallel to the flow direction
of pellet stream. Alternatively, e.g. when pellets possess
sufficient wear resistance, then the section (A) of the invention
may also be arranged to rotate 360.degree. around its axis that is
parallel to the flow direction of the pellet stream, in addition to
movement caused by means (2).
[0097] The total time period required for the first mixing step (A)
in the first mixing apparatus (A) of the invention may vary and can
be e.g. less than 10 minutes, such as less than 7 minutes,
preferably less than 5 minutes, more preferably less than 4
minutes. In one further preferable embodiment of the invention, the
mean residence time of a pellet in section (A) is very short, less
than 3 minutes, preferably less than 2, more preferably less than 1
minute, such as between 5 and 45 sec. Depending on the embodiment,
as short mean residence time of a pellet as within the range of
5-30 sec, may also be sufficient.
[0098] The equipment of the invention may comprise one or more of
said apparatus (A), or said apparatus (A) of the invention may
comprise one or more first mixing sections (A), which apparatuses
(A) and/or sections (A) are arranged in series and/or in
parallel.
[0099] The inner surfaces of the first mixing section (A) are
advantageously polished, for example polished and/or even
electro-polished, in order to reduce abrasion of the pellets.
[0100] As to the mixing means (2) of the apparatus (A) of
invention, said vibration means (2a) and oscillation means (2b) of
the first mixing section (A) can be any means that causes the
pellet stream to vibrate and, respectively, oscillate in order to
transfer and mix the polymer pellet stream for distributing said
liquid among the pellets. Said means (2a) and (2b) may be provided
in one operating system that both vibrates and oscillates.
Preferably, said means (2) is a device arrangement which causes the
pellet stream vibrate and oscillate. Suitable means for
vibration/oscillation are well known and can be e.g. any
commercially available mechanical and/or electromechanical means
that can be arranged to the first mixing section (A). Preferably
such means are arranged outside, externally, said section (A) to
cause the section (A) to at least vibrate and, optionally also
oscillate, and thereby to cause the pellet stream to vibrate and
optionally oscillate within said section (A). Preferably, in this
embodiment no mechanical mixing means, moving or static, are
present in said first mixing section (A).
[0101] The degree of vibration/oscillation is controlled by
controlling the frequency, amplitude and direction of
vibration/oscillation and can easily be adjusted to suitable values
by a man skilled in the art. The appropriate degree of
vibration/oscillation may vary between different embodiments of the
invention depending on, for instance, the capacity (volume) of the
first mixing section (A), the flow of polymer pellets, the type of
polymer, the flow of the liquid, the type of the further
component(s) present in the liquid etc.
[0102] As to fluidisation means (2c) of the apparatus (A) of the
invention, fluidisation of the pellet stream in the first mixing
section (A) of the invention is effected by fluidisation means (2c)
of the polymer pellets for moving/mixing the pellets stream in a
fluidization medium, selected from a gas, such as air or N.sub.2,
or a liquid medium. Fluidization means (2c) can be operated in a
pneumatic or hydraulic manner, depending on the used fluidization
medium, in order to suspend, transfer and mix said fed polymer
pellets and applied liquid along said section (A) and towards the
outlet (4) as well known in the art. Preferably said fluidisation
medium is inert.
[0103] In a further embodiment of the invention, the first mixing
section (A) is caused to vibrate and/or oscillate by application of
mechanical and/or electromechanical means (2a) and/or (2b) and
additionally the polymer pellets and applied liquid(s) are caused
to fluidise by suspending them in a moving liquid or gas, such as
air. The introduction of gas and/or liquid may be operated e.g. by
hydraulic means (2c), respectively, by pneumatic means (2c).
[0104] As to at least one application means (3) of the apparatus
(A) of the invention, such means (3) for applying, i.e. adding,
said further component(s), e.g. as said liquid, onto the polymer
pellets can be arranged prior to said first mixing apparatus (A),
at the inlet (1) of said apparatus (A) or within the first mixing
section (A) of said apparatus (A). In case the apparatus (A)
comprises two or more of said means (3), these can be arranged in
different positions within said apparatus (A). Preferably at least
one application means (3) of the invention is arranged within said
inlet (1) of the apparatus (A) and/or within said first mixing
section (A). Also preferably when said one or more means are within
said section (A), then preferably at least one of said means (3) is
positioned very close to said inlet (1).
[0105] In case fluidisation means (2c) are used alone or in any
combination with means (2a) and/or (2b) the direction of the pellet
stream is essentially horizontal as defined above and again the
individual pellets in the horizontal pellet stream transfer can
move in any direction.
[0106] It is thus possible to arrange one or more application
points along the first mixing section (A) for adding said further
component(s) at different positions of said section (A). Moreover,
in case two or more further components are added via application
means (3) of the invention, then these may be added together or one
or more of said components may be added separately or as a mixture.
Such separate application(s) may occur, as evident, from different
or same application means (3), from different positions within the
apparatus (A) or at different time points during the first mixing
step (A), or in any combinations thereof.
[0107] Furthermore, at least one of said application means (3),
when present in first mixing section (A) and/or inlet (1) of said
apparatus (A), is preferably arranged to extend at least partly
within the polymer pellet stream. I.e. said means (3) in such case
is in direct contact with the polymer pellet stream, so that the
addition of said further component(s) occur within said stream. In
this arrangement the liquid(s) is/are applied within the continuous
stream of flowing polymer pellets. In this embodiment said
application means (3) may then be self-cleaning due to the stream
of moving pellets around it.
[0108] Thus said means (3) for applying said further component(s)
onto the polymer pellets may comprise one or more application units
provided at different locations, preferably at different locations
within the first mixing section (A), through which the liquid(s) is
applied onto the polymer pellets.
[0109] Furthermore, the application unit(s) can be in any form,
such as in T-, X- or U-form.
[0110] Each of those application units preferably comprise one or
more nozzle(s). The nozzle(s) can be arranged e.g. along said T-,
X- or U-form of the application unit. "Nozzle" means herein any
application device comprising one or more holes, called herein
injection holes, through which the liquid is applied by any means,
such as by spraying, by injecting, by dripping etc, as known in the
art, e.g. an injection nozzle.
[0111] Preferably, each nozzle comprises one or more injection
holes, preferably a plurality of injection holes, through which the
liquid is applied onto the pellets. The holes can be positioned in
any direction, for example with the flow or against the flow etc.
The injection holes of the nozzle can be arranged in any
configuration. As examples a T-, X-, O- or U-configuration could be
mentioned, wherein the injection holes can be arranged in any
direction to apply the liquid e.g. against or parallel with the
pellet stream flow.
[0112] The application units and thus nozzles of said application
means (3) can be positioned along the first mixing apparatus (A),
preferably along the first mixing section (A). Preferably said
application unit part of the application means (3) are positioned
within the pellet stream.
[0113] The liquid can be applied either intermittently or
continuously onto the polymer pellets.
[0114] When more than one further components are to be applied
through the application means these can be applied separately or as
a mixture. Moreover, if more than one further components are to be
applied, these can be added via the same or different application
units. Accordingly, all or part of the components to be
incorporated into the pellets are applied together as a mixture on
to the pellets or each or part of said components are applied onto
said pellets via one or more application unit(s) of said
application means (3).
[0115] It shall be noted that the means (3) for applying said
liquid phase preferably lacks any moving parts in order to avoid
abrasion of polymer pellets.
[0116] Furthermore, the degree of filling of said pellets is high
in the equipment of the invention, in particular in the first
mixing section (A), preferably especially in case of continuously
operated equipment. The high degree of filling ensure that minimal
or no dead zones will be present and also contributes to the
self-cleaning properties. The pellet stream may fill more than 20%,
preferably more than 35%, more preferably 50% or more, of the
volume of the first mixing section (A).
[0117] In one embodiment the feed ratio of the further
component(s), preferably of said liquid, and the polymer pellets in
the equipment of the invention is not limited. As an example, the
weight ratio of (pellet feed):(liquid feed) can vary depending on
the further components and fed pellets, and may be e.g. in the
range of 99.997:0.001 to 50:50, preferably in the range of 99.5:0.5
to 70:30, more preferably between 99.0:1.0 to 85:15.
[0118] It shall be noted that the equipment, in particular the
first mixing section (A), according to the invention is preferably
a closed equipment with minimal leakage to the surroundings,
thereby being more environmentally friendly.
[0119] As a consequence of the efficient distribution of said
liquid between and within said pellets in said apparatus (A) of the
invention, the need for additional mixing in static mixing section
(B) can be markedly reduced or even avoided. Furthermore, the first
mixing section (A) may be arranged to result in essentially
homogeneous distribution and absorption of said one or more further
components within the pellets that said drying step in section (C)
may be shortened markedly. In some embodiments section (C) could
even be avoided.
[0120] If the equipment of the invention comprises said optional
static mixing section (B), a rather simple construction thereof can
be used (in comparison to, for instance, the static mixer
comprising deviating wings, supporting legs and baffles as
described in WO 00/38895).
[0121] As used herein "static mixing section B" lacks preferably
any mechanically moving mixing parts, whereby polymer dust
generation due to abrasion can preferably be reduced.
[0122] The static mixing section (B) of the invention, if present,
comprises means for changing the flow direction of the pellets in
said continuous flow of pellets. In particular, said mixing section
comprises one or more tubular bends (5), more specifically two or
more bends (5) where adjacent bends (5) are connected by an
intermediate part inclined downwards, for changing the flow
direction of the pellets. Thus, a plurality of bends (5) are
suitably arranged in a downward spiral manner causing the pellets
to flow by gravity through the bends. Said structure could also be
described as a zig-zag shaped structure.
[0123] Preferably, the bends (5) have a bending degree, with regard
to the longitudinal axis of the mixing section (B), of at least
20.degree., such as within the range of 45-90.degree..
[0124] The distance between each bend (5) can be equal or of
varying length. The angle of the bends (5) themselves should be
30-90.degree. (60-150.degree.). The bends (5) are placed with the
needed angle to provide an easy flow of pellets.
[0125] A suitable volume of the static mixing section (B) in
relation to the flow of the pellets, the type of polymer, the type
of substance in liquid phase, the flow of said substance, and the
volume and degree of vibration of the first mixing section (A) can
be easily determined by a man skilled in the art.
[0126] It shall be noted that the static mixing section (B) of the
invention can additionally comprise further mixing means typically
inside said mixing device. Such further mixing means include static
mechanical mixing means, such as baffles, etc, supported therein,
but it is not necessary in order to obtain a sufficient degree of
mixing. If present, preferably static mixing means, such as
baffles, may be arranged to deviate pellets flowing in the central
zone of the mixing section to the peripheral zone and vice versa.
Preferably, apart from the above described bends the static mixing
means (B) does not comprise further static mixing means.
[0127] The drying section (C), if present, can ensure varying
degree of homogenisation of the further component(s), e.g. from a
complete absorption to an essentially complete homogenisation, as
desired.
[0128] Said optional drying section (C) of the equipment of the
invention, if present, is preferably carried out in elevated
temperature. The polymer pellet stream coming from section (A), or,
if static mixing section (B) is present, from section (B), can be
preheated before entering to drying section (C) and/or during the
drying within section (C). The temperature during the drying step
(C) may vary and is typically above the solidification point of
said liquid and/or said added further component(s).
[0129] Further preferably, the operating temperature in each of
said section (C) may be selected to be such that temperature of the
polymer material of said fed pellets is kept below the melting
point of the major polymer component of said fed pellet material,
preferably at or above ambient temperature. More preferably, the
temperature of said fed polymer pellets in said optional section
(C) is kept at least 10.degree. C., preferably at least 15.degree.
C., more preferably at least 20.degree. C., below the melting point
of the major polymer component of the polymer material of said fed
pellets, as evident for a skilled person. Moreover, the temperature
in the drying section (C) is preferably above ambient temperature,
in particular above 30.degree. C., more particularly above
40.degree. C., and most particularly above 50.degree. C.
[0130] The polymer pellets are advantageously flown by gravity
through the drying section (C). Such flow may occur in one or more
drying tanks either in parallel or in series, in a known
manner.
[0131] The residence time is not limited and can vary depending on
the produced pellets and the above mentioned desired degree of
distribution of said further component(s). The polymer pellets may
usually be kept in the drying section (C) in each drying tank e.g.
for about <24 h, more preferably <20 h, still more preferably
<16 h.
[0132] In embodiment where said drying section (C) of the invention
is carried out in two drying tanks arranged in series, the period
in the first drying tank is preferably form 0.05 to 16 h, or even
less than 12 h. In turn, the time period in the second drying tank
is then preferably up to 24 h, more preferably <20 h, still more
preferably <16 h, and most preferably form 0.05 to 12 h, e.g.
0.1-12 h.
[0133] In case of two or more tanks of said drying section (C), the
temperatures can be the same or different.
[0134] The polymer material for said pellets usable in the
equipment or process of the invention is not limited and includes
any polymer or polymer composition which can incorporate one or
more desired further components from a liquid phase within the
pellet structure.
[0135] Examples of suitable polymers for pellets usable in the
equipment or process of the invention are given below only as
non-limiting options. Accordingly, the polymers usable in the
equipment and process of the present invention can thus be polymers
of any type.
[0136] In a preferred embodiment, said polymer is a polyolefin
which can be a homopolymer of an olefin or a copolymer of an olefin
with one or more comonomers.
[0137] As one preferable group of said polyolefins includes
homopolymer of ethylene or copolymer of ethylene with one or more
comonomers, such as 1) a branched polyethylene homo- or copolymer
produced in high pressure by radical polymerisation and well known
as low density polyethylene (LDPE) homo or copolymer or 2) a linear
polyethylene homo- or copolymer produced by low pressure
polymerisation using a coordination catalyst, such as well known
plastomers, linear very low density polyethylene, linear low
density polyethylene (LLDPE), medium density polyethylene (MDPE) or
high density polyethylene (HDPE), 3) polypropylene polymers,
including homopolymers and random polymers of polypropylene and
heterophasic copolymer of propylene.
[0138] Said ethylene polymers are very preferred as said polymer
material of said fed pellets for the equipment and for the process
of the invention, and a further preferable subgroup thereof is said
1) LDPE homopolymer or equally preferable subgroup thereof is said
1) LDPE copolymer with one or more comonomers including a) C3 or
higher alpha-olefin copolymer(s), b) polar comonomers, c)
silane-group containing comonomers, d) polyunsaturated comonomers,
e.g. a comonomer with at least two double bonds, such as diene
comonomers, or any combinations of comonomers (a)-(d). Such
comonomers a)-d) are well known in the art. High pressure
polymerisation for producing LDPE homopolymers and copolymers is a
well known technology in the polymer field and can be effected in a
tubular or in an autoclave reactor, preferably, in a tubular
reactor. High pressure polymerisation is typically effected at 80
to 350.degree. C. using a pressure of 100-400 MPa. Further details
about high pressure radical polymerisation are given in WO
93/08222.
[0139] Further preferably, said 1) LDPE copolymers are the 1) LDPE
copolymers of ethylene with b) a polar group containing
comonomer(s) and, optionally, with other comonomer(s). As examples
of comonomers having polar groups may be mentioned the following:
(a) vinyl carboxylate esters, such as vinyl acetate and vinyl
pivalate, (b) (meth)acrylates, such as methyl(meth)acrylate,
ethyl(meth)acrylate, butyl(meth)acrylate and
hydroxyethyl(meth)acrylate, (c) olefinically unsaturated carboxylic
acids, such as (meth)acrylic acid, maleic acid and fumaric acid,
(d) (meth)acrylic acid derivatives, such as (meth)acrylonitrile and
(meth)acrylic amide, and (e) vinyl ethers, such as vinyl methyl
ether and vinyl phenyl ether.
[0140] Amongst these LDPE copolymer of ethylene with one or more of
vinyl esters of monocarboxylic acids having 1 to 4 carbon atoms,
such as vinyl acetate, and (meth)acrylates of alcohols having 1 to
4 carbon atoms, such as methyl (meth)acrylate, ethyl (meth)acrylate
and butyl (meth)acrylate are preferred. More preferably said LDPE
copolymer suitable for said polymer material of said fed pellets
for use in said equipment and pellet preparation process of the
invention is a LDPE copolymer of ethylene with one or more of vinyl
acetate, methyl acrylate, ethyl acrylate or butyl acrylate,
preferably a LDPE copolymer of ethylene with methyl acrylate, a
LDPE copolymer of ethylene with ethyl acrylate or a LDPE copolymer
of ethylene with butyl acrylate, or any mixture thereof.
[0141] The term "(meth)acrylic acid" and "(meth)acrylate" are
intended to embrace both acrylic acid and methacrylic acid and,
respectively "methacrylate" and "acrylate".
[0142] The amount of said polar comonomer(s) in said LDPE copolymer
is not limited and may be e.g. up to 70 wt %, preferably 0.5 to 35
wt %, more preferably 1 to 30 wt %, based on the total amount of
said LDPE copolymer.
[0143] Moreover, said preferred polyolefin, preferably
polyethylene, more preferably said 1) LDPE homopolymer or 1) said
LDPE copolymer, which said 1) LDPE copolymer is more preferably
said 1) LDPE copolymer of ethylene with b) a polar group containing
comonomer(s) as defined above, may optionally further comprise
unsaturation, i.e. be an unsaturated polyolefin, preferably an
unsaturated polyethylene, more preferably an unsaturated 1) LDPE
homopolymer or an unsaturated 1) LDPE copolymer, which said
unsaturated 1) LDPE copolymer is more preferably an unsaturated 1)
LDPE copolymer of ethylene with b) a polar group containing
comonomer(s) as defined above, whereby said unsaturation is
preferably provided by copolymerising olefin units, preferably
ethylene units, with units of one or more of said d)
polyunsaturated comonomer(s) and/or by using a vinyl/double bond
introducing chain transfer agent, such as an alpha-olefin, such as
propylene. Said unsaturated 1) LDPE homopolymer when produced
copolymerising of ethylene with said d) polyunsaturated
comonomer(s) is actually 1) LDPE copolymer of ethylene with said d)
polyunsaturated comonomer(s), but is referred herein as unsaturated
1) LDPE homopolymer to differ it from said unsaturated 1) LDPE
copolymer which further comprises other comonomers.
[0144] Such unsaturated polymers are well known and described e.g.
in WO 93/08222, EP1695996 or WO2006/131266. Typically said
unsaturated polyolefins have a double bond content of more than 0.1
double bonds/1000 C-atoms.
[0145] As to said preferable polyolefins, more preferably
polyethylene, suitable as said polymer material for said fed
pellets for said equipment and for the pellet preparation process
of the present invention include a polyolefin polymer, preferably
homo or copolymer of ethylene, wherein silane-groups containing
compounds are incorporated by grafting using an unsaturated silane
compound or by copolymerisation of said c) silane-group containing
comonomer units, which grafting and copolymerisation are well known
methods in the art. Copolymerising said b) silane-group containing
comonomer units with olefin units, preferably with ethylene units,
results naturally to a copolymer. Said silane-containing
polyolefin, is preferably polyethylene, more preferably said 1)
LDPE, as defined above, comprising said silane-containing
compounds, which are incorporated to said polyolefin by
copolymerising or by grafting, and optionally further comprising
other comonomer(s), which optional further comonomer is preferably
one or more of said b) polar comonomer(s) as defined above, and/or,
further optionally, further comprising unsaturation provided by
copolymerising said d) polyunsaturated comonomer units and/or by
using a vinyl/double bond introducing chain transfer agent, as
defined above.
[0146] Also 2) linear ethylene polymers prepared using said low
pressure polymerisation are very suitable for the invention. As an
example plastomers, VLDPE, LLDPE, MDPE and HDPE polymers can be
mentioned. They can be produced in a known manner in a single or
multistage processes using one or more of e.g. Ziegler-Natta
catalysts, single site catalysts, including metallocenes and
non-metallocenes, and Cr-catalysts. All said catalysts are very
well known in the field. The multistage process includes any
combinations of polymerisation processes, such as slurry
polymerisation, solution polymerisation, gas phase polymerisation,
or any combinations thereof, in any order.
[0147] Generally, polymers that are usable in the present invention
include any known polymers, e.g. commercially available polymers,
or they can prepared in a known manner according to or analogously
to polymerisation process described in the literature.
[0148] Naturally any mixtures of polymers can also be used in the
pellets useful for the equipment and process of the invention.
[0149] As to one or more further components usable in the liquid of
the equipment or the process on the invention, said further
component(s) is/are not limited and include any component suitable
for providing e.g. one or more of a chemical, physical, mechanical,
functional or processing property to the produced polymer pellet or
to a product manufactured from the produced polymer pellets, as
well known in the art.
[0150] Examples of suitable one or more further components usable
in the equipment or method of the invention are given below only as
non-limiting options. Herein by "selected from one or more of" is
naturally understood that said liquid can comprise one or more
additives within an additive group having a same function, e.g.
from one or more antioxidants, and/or additives between different
additive groups, such as crosslinking agents, scorch retardants and
antioxidants.
[0151] Accordingly, examples of such one or more further components
are e.g. those conventionally used or can be used analogically
thereto in different end applications of polymers i.a. one or more
of crosslinking agents, crosslinking co-agents (boosters),
antioxidants, thermal stabilisers, light stabilisers, voltage
stabilisers, water tree retardant agents, UV stabilisers,
processing aids, lubricants, flame retardants, scorch retardants,
nucleating agents, acid scavengers, inorganic fillers and organic
fillers such as carbon black, and any mixtures thereof.
[0152] The amount said further component(s) depends, of course, on
the component and the desired effect, and as an example e.g. each
further component may be present in the pellets in amount of e.g.
less than 15.0 wt %, suitably less than 10.0 wt %, preferably less
than 6.0 wt %, more preferably less than 5.0 wt %, such as less
than 3.5 wt % and preferably within the range of 0.005 to 3% of
total weight of the polymeric pellets. However, some additives or
fillers, such as flame retardants and inorganic and organic fillers
may, if added to pellets, be added in higher amounts, to obtain
pellets comprising such additives in an amount of up to 80 wt %,
e.g. up to 50 wt % of the total weight of the polymeric pellets.
Typically, such fillers which are used in higher amounts are
already present in the pellets.
[0153] Said one or more further component in liquid phase is
advantageously at least a crosslinking agent.
[0154] As mentioned above a crosslinking agent can be selected
based on the used crosslinking technology, e.g. peroxide
crosslinking technology or silane crosslinking technology. Both
peroxide and silane crosslinking technologies and the crosslinking
agents used in these technologies are well known and documented in
the polymer literature.
[0155] As an example of crosslinking agents for peroxide
crosslinking technology, in particular, the crosslinking agent
contains at least one --O--O-- bond or at least one --N.dbd.N--
bond. Non-limiting examples of crosslinking agents are organic
peroxides, such as di-tert-amylperoxide,
2,5-di(tert-butylperoxy)-2,5-dimethyl-3-hexyne,
2,5-di(tert-butylperoxy)-2,5-dimethylhexane,
tert-butylcumylperoxide, di(tert-butyl)peroxide, dicumylperoxide,
bis(tertbutylperoxyisopropyl)benzene,
butyl-4,4-bis(tert-butylperoxy)-valerate,
1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane,
tert-butylperoxybenzoate, dibenzoylperoxide,
bis(tert-butylperoxyisopropyl)benzene,
2,5-dimethyl-2,5-di(benzoylperoxy)hexane,
1,1-di(tert-butylperoxy)cyclohexane, 1,1-di(tert
amylperoxy)cyclohexane, or any mixtures thereof.
[0156] Examples of crosslinking agents for silane crosslinking
technology that are usable in the present invention, e.g. well
known silanol condensation catalysts, i.a. those mentioned in
EP736065, EP1309631 or EP1309632, can be mentioned.
[0157] Examples of crosslinking boosters usable as said one or more
further components of the invention are compounds having one or
more double bonds or one or more vinyl- or allyl group, such as
triallylcyanurate, triallylisocyanurate, and di-, tri- or
tetra-acrylates.
[0158] As antioxidants and thermal stabilisers usable as said one
or more further components of the invention, i.a. phenol-based
antioxidants/stabilisers, amine-based antioxidants/stabilisers,
hindered amine light antioxidants/stabilizers (HALS), thioesters,
phosphates, metal chelating agents, and any mixtures thereof, such
as sterically hindered or semi-hindered phenols, optionally
substituted with functional group(s), aromatic amines, aliphatic
sterically hindered amines, organic phosphates, thio compounds, and
mixtures thereof, can be mentioned.
[0159] Examples of scorch retardants usable as said one or more
further components of the invention are i.a.
2,4-diphenyl-4-methyl-1-pentene, substituted or unsubstituted
diphenylethylene, quinone derivatives, hydroquinone derivatives,
monofunctional vinyl containing esters and ethers, or mixtures
thereof.
[0160] As mentioned, said one or more further components usable in
the present invention can be added as solids or can be dissolved,
emulgated or suspended in a liquid medium, which can be e.g.
solvent, a further one or more component which is in liquid form or
a diluting agent, or any combination thereof, that, as evident for
a skilled person, is suitable for forming a liquid solution or
suspension with the further component(s) to be applied in said
liquid onto polymer pellets using the equipment or process
according to the invention. Naturally also said one or more further
components can be used in a molten state.
[0161] The invention further provides polymer pellets comprising
one or more polymer components and one or more further components
incorporated into said pellets by applying a liquid to said
pellets, wherein said pellets are produced according to the process
and/or equipment of the invention.
[0162] In one embodiment, a process of the invention for producing
polymer pellets for wire and cable applications is provided.
Furthermore, a use of said equipment of the invention as defined
above for producing polymer pellets for wire and cable
applications, such as for one or more layers of a cable which
comprises a conductor and one or more layers surrounding said
conductor. Also polymer pellets for wire and cable applications
obtainable by said process and/or equipment of the invention are
provided.
[0163] In one preferable embodiment, a process of the invention for
producing polymer pellets for crosslinkable articles using said
equipment of the invention is provided. Said crosslinkable article
is preferably a cable comprising a conductor and at least one
crosslinkable layer surrounding said conductor, wherein said at
least one layer is obtainable by using said polymer pellets of the
invention.
[0164] The term "conductor" means herein above and below that the
conductor comprises one or more wires. Moreover, the cable may
comprise one or more such conductors. Preferably the conductor is
an electrical conductor.
[0165] The pellets of the invention are most preferably used for
power cable applications, e.g. for the known low voltage, medium
voltage, high voltage or extra high voltage cable applications. In
one embodiment a process of the invention for producing polymer
pellets for one or more crosslinkable layers of a cable as defined
above is provided, wherein said one or more crosslinkable layers
are selected from one or more of an insulation layer, a
semiconductive layer or a jacketing layer.
[0166] As well known for a skilled person said semiconductive layer
comprises further a carbon black which is preferably already
present in the pellets when fed to an first mixing apparatus (A) of
the invention. In a preferable embodiment, the semiconductive layer
composition may have a volume resistivity of less than 500000
.OMEGA. cm, when measured at 23.degree. C. and/or 90.degree. C.,
preferably of less than 100000 .OMEGA. cm, when measured at
23.degree. C. and/or 90.degree. C. Alternatively, when the DC
volume resistivity is measured according to ISO 3915 using a
crosslinked plaque, then a preferable semiconductive layer
composition may have a volume resistivity of less than 5000 .OMEGA.
cm, preferably of less than 1000 .OMEGA. cm, such as of less than
500 .OMEGA. cm, more preferably of less than 100 .OMEGA. cm, when
measured at 23.degree. C., or of less than 50000 .OMEGA. cm,
preferably of less than 10000 .OMEGA. cm, such as of less than 5000
.OMEGA. cm, more preferably of less than 1000 .OMEGA. cm, when
measured at 90.degree. C.
[0167] In said preferable embodiment for producing crosslinkable
pellets of the invention, the polymer material can be selected from
e.g. any of the polymer materials exemplified above, more
preferably from polyolefin, even more preferably from homopolymer
or copolymer of ethylene, most preferably from said 1) LDPE
homopolymer or said 1) LDPE copolymer, which 1) LDPE copolymer is
preferably said 1) LDPE copolymer of ethylene with b) a polar group
containing comonomer(s) as defined above, which 1) LDPE homo and
copolymer are produced in high pressure by radical polymerisation,
as defined above. Said preferred subgroup of polyolefin, more
preferably subgroup of 1) LDPE homopolymer or said 1) LDPE
copolymer, which 1) LDPE copolymer is preferably said 1) LDPE
copolymer of ethylene with b) a polar group containing comonomer(s)
as defined above, for producing crosslinkable pellets of the
invention may optionally further comprise unsaturation, i.e. be an
unsaturated polyolefin, preferably an unsaturated 1) LDPE
homopolymer or an unsaturated 1) LDPE copolymer, which unsaturated
1) LDPE copolymer is preferably an unsaturated 1) LDPE copolymer of
ethylene with b) a polar group containing comonomer(s) as defined
above, whereby said unsaturation is preferably provided by
copolymerising olefin units, preferably ethylene units, with units
of one or more of said d) polyunsaturated comonomer(s) and/or by
using a vinyl/double bond introducing chain transfer agent, such as
an alpha-olefin, such as propylene. Said unsaturated 1) LDPE
homopolymer when produced copolymerising of ethylene with said d)
polyunsaturated comonomer(s) is actually 1) LDPE copolymer of
ethylene with said d) polyunsaturated comonomer(s), but is referred
herein as unsaturated 1) LDPE homopolymer to differ it from said
unsaturated 1) LDPE copolymer which further comprises other
comonomers.
[0168] In such embodiment for providing crosslinkable pellets and
crosslinkable articles, said liquid to be applied onto pellets in a
manner as defined above comprises one or more crosslinking agents
which is/are selected e.g. from crosslinking agents as defined
above, preferably at least one peroxide crosslinking agent.
Preferably said liquid comprises, in addition to crosslinking
agent(s), also one or more further additives including one or more
crosslinking boosters, scorch retardants or antioxidants, which
each can be e.g. as defined above, or, naturally, any mixtures
thereof.
[0169] Furthermore, the invention provides a process for producing
a cable comprising a conductor and one or more layers surrounding
said conductor, wherein said one or more layers is/are selected
from one or more of an inner semiconductive layer, an insulation
layer, an outer semiconductive layer or a jacketing layer, if
present, in that order, preferably from a crosslinkable insulation
layer, a crosslinkable semiconductive layer or a crosslinkable
jacketing layer, and wherein said one or more layers are obtainable
by polymer pellets produced according to a process of the
invention. In this embodiment said one or more of the crosslinkable
insulation layer, the crosslinkable semiconductive layer or the
crosslinkable jacketing layer is preferably crosslinkable by
radical reaction.
[0170] A process for producing a crosslinkable cable comprising a
conductor and at least one crosslinkable layer surrounding said
conductor is also provided, wherein said process comprises steps of
producing a crosslinkable polymer composition for said at least one
crosslinkable layer using polymer pellets that are produced
according to a process, as defined above or below in claims, and
extruding said at least one crosslinkable layer on a conductor
using the obtained polymer composition. Preferably, in this
embodiment of the process of the invention said at least one
crosslinkable layer is selected from layers including an inner
semiconductive layer, insulation layer or outer semiconductive
layer.
[0171] In a further embodiment of the process of invention said
process comprises a further step of crosslinking, preferably by
radical reaction, said at least one crosslinkable layer obtainable
by the process, as defined above or in claims below, by subjecting
said cable to a crosslinking conditions, preferably to an elevated
temperature. Such crosslinking temperatures are within the skills
of a skilled person.
[0172] Naturally the invention covers also a crosslinkable article,
preferably a crosslinkable cable as well as a crosslinked article,
preferably a crosslinked cable, which is obtainable by said process
of the invention as defined above or in claims below.
[0173] The above mentioned cables, layers, crosslinkable layers and
crosslinking methods are well known in the wire and cable field and
well documented in the literature and thus need not to described
herein in details.
[0174] The invention will now be illustrated by means of the
following non-limiting examples:
EXAMPLES
[0175] For Comparative Example 1 and Examples 1 and 2 of the
invention a known low density polyethylene homopolymer with a
MFR.sub.2 of 2 g/10 min and a density of 922 kg/m.sup.3 was used.
For Example 3, a polymer composition of a blend of low density
polyethylene homopolymer and a known poly(ethylene-co-acrylate) was
used which had a MFR.sub.2 of around 3 g/10 min and a density of
926 kg/m.sup.3.
[0176] The weight ratio between polyethylene and DCP in Comparative
example 1 and in Example 1 and 2 of the invention were the same and
in conventionally used amounts. In Example 3 of the invention
similar amounts and ratios of pellets and DCP was used and
additionally a further additive was added as described below.
Comparable pellet/additive feeds (kg/h) were used in Examples of
the invention and in Comparative example.
[0177] In Example 1, 2 and 3 of the invention the same first mixing
section (A) according to the invention was used and in said Example
1 and 3 of the invention additionally a static mixer (B) according
to the invention was used. In comparison of the cross sectional
areas (Example 4) the same equipment as in Example 1 of the
invention and in Comparative example 1 was used.
[0178] A so-called zig-zag blender was used in Comparative example
1. It was a commercially available blender and comprised a
360.degree. cylindrical entrance section having an inner diameter
which was 3 times larger than the inner diameter of section (A) in
Example 3 of the invention; and 4 times larger than the inner
diameter of section (A) in Example 1 and 2 of the invention; and 3
times larger than the inner diameter of section (B) in Examples 1
and 3. The total volume of the zig-zag blender of the Comparative
example 1 was about 5.5 times larger than the volume of the first
mixing section (A) of Example 3 of the invention and about 4 times
larger volume than the total volume of first mixing section (A) and
static mixing section (B) of the Example 3 of the invention. The
total volume of the zig-zag blender of the Comparative example 1
was about 15 times larger than the volume of the first mixing
section (A) of Example 1 and 2 of the invention and about 7 times
larger volume than the total volume of first mixing section (A) and
static mixing section (B) of the Example 1 of the invention.
[0179] The total mean residence time of a pellet in the equipment
(A+B) of Examples 1, the equipment (A) of example 2 and the
equipment (A+B) of Example 3 of the invention and in the zig-zag
blender of Comparative Example 1 were comparable in that the
residence time in each example was chosen to be a time period which
resulted in pellets a distribution of the peroxide that is
comparable with each example.
[0180] In said zig-zag blender of comparative example and in said
static mixer (B) of Example 1 and Example 3 of the invention the
pellets were flown through a plurality of bends.
[0181] The same temperature between 50.degree.-80.degree. was used
in said zig-zag blender of Comparative example and in said first
mixing section (A) and optional static mixing section (B) of
Examples of the invention, during each compared test run.
[0182] 25 pellets were taken at two time points during each test
run, each time when stable conditions had been reached in the
blender. The pellets were collected in pre-weighed vials with
cover, one pellet in each vial. The 25 pellets from each of the two
sample take-outs of a test run were taken immediately from the
pellet stream coming from the outlet of the blender.
[0183] Then the vials with pellets and cover were weighed again and
the weight of each pellet was calculated.
[0184] 1 ml n-hexane was added to each vial. Then the pellets were
extracted for 5 h at 55.degree. C. After extraction, the solvent
was analysed by HPLC and the content of dicumyl peroxide in the
pellets was then calculated.
[0185] The test procedure gives an indication of the distribution
of peroxide between the pellets in each test and can be used for
comparing pellet samples prepared in examples of the invention and
in the comparative example.
Comparative Example 1
[0186] Said polyethylene pellets and dicumyl peroxide (DCP) were
added to said zig-zag blender.
[0187] The peroxide was applied by spraying through one nozzle
provided with several injection holes positioned in the feeding
pipe within the entrance part part.
[0188] Pellets were collected from the pellet stream coming out of
the zig-zag blender and analysed as described above.
[0189] The average content of dicumyl peroxide in a pellet was
found to be 1.38% by weight (standard deviation .+-.0.16, relative
standard deviation 11.4%, based on 2 tests, each including 25 test
pellets).
Example 1 of the Invention
[0190] Said polyethylene pellets were fed to an essentially
horizontally arranged pipe (A) of polished stainless steel having a
circular cross-section
[0191] The pipe (A) was caused to vibrate with a frequency of 60 Hz
using a commercially available vibration generator (means (2)).
This vibration caused the pellets to flow within the pipe (A).
[0192] Dicumyl peroxide (DCP) was added through a T-shaped nozzle
(3) positioned within the vibratory pipe (A) close to the inlet (1)
thereof.
[0193] The pellets were passed from the vibrating pipe (A) to said
static mixer (B).
[0194] Pellets were collected from the pellet stream coming out of
(B) and analysed as described above.
[0195] The average content of dicumyl peroxide in a pellet was
found to be 1.52% by weight (standard deviation .+-.0.25, relative
standard deviation 17%, based on two tests, each including 25 test
pellets).
[0196] Thus, it was shown that an equipment according to the
invention can handle the same production capacity (i.e. volume of
pellets) and result in a similar distribution of dicumyl peroxide
between pellets even though the volume of this equipment was much
smaller than the volume of the zig-zag blender used in the
Comparative Example 1, as given above.
[0197] Furthermore, the mean residence time period of the pellets
spent in the equipment was about 50% shorter than the corresponding
time period of Comparative Example 1.
[0198] Consequently, the equipment and method according to the
invention was shown to be much more efficient than the zig-zag
blender of Comparative Example 1, i.e. a faster distribution of
said further component in liquid phase among the pellets with the
comparable level of evenness in distribution between the pellets
while using an equipment with a much smaller volume.
Example 2 of the Invention
[0199] Example 2 is to exemplify an optional set up where a first
mixing section (A) is used, but without a static mixer section (B).
The set-up as described in Example 1 was used, i.e. T-shaped
addition unit (3) (the same as described above), but no static
mixing section (B).
[0200] The average content of dicumylperoxide in a pellet was found
to be 1.16% by weight (standard deviation .+-.0.37, relative
standard deviation 32%, based on two tests, each including 25 test
pellets). This is a set-up that provides an industrially feasible
solution with a distribution of the one or more component(s) within
the pellets that would be sufficient in many end applications.
Example 3 of the Invention
[0201] A pre-blended mixture of DCP and a known crosslinking
additive (CA) in a weight ratio of DCP:CA of around 5:1 was added
via a X shaped nozzle (3) positioned in the inlet (1) of the first
mixing section (A).
[0202] For these analyses 3 sample take-outs, each of 25 pellets
were collected. This time 1 ml n-hexane was added to each vial and
the extraction was done at 69.degree. C. and for 2 h. The average
content of dicumyl peroxide in a pellet was found to be 1.71% by
weight (standard deviation .+-.0.18, relative standard deviation
10.7%, based on 25 test pellets). The results were the average
values of three test series, each consisting of 25 pellets.
[0203] The average content of said (CA) in a pellet was found to be
0.38% by weight (standard deviation .+-.0.042, relative standard
deviation 11.0%, based on three tests, each including 25 test
pellets).
Example 4
[0204] Comparison of cross sectional areas of the blender of
comparative example and of the equipment of the inventive
examples.
[0205] The inlet part of the zig-zag blender in Comparative example
1 is compared with first mixing section (A) in Example 3. This
means that the cross sectional area of the device (A) described in
Example 3 has about 9 times smaller cross sectional area.
[0206] The diameter of the bend part of zig-zag blender in
Comparative example 1 is compared with the static mixing section
(B) in Example 3. This means that the cross sectional area of the
device (B) described in Example 3 has about 9 times smaller cross
sectional area and thus the throughput per cross sectional area is
9 times higher in the device described in Example 3.
* * * * *