FORM 2
THE PATENTS ACT, 1970
(Act 39 of 1970)
COMPLETE SPECIFICATION
(See Section 10; Rule 13)
10
Title: “Method and a Device for Preparation of a Hybrid
15 Filler consist of Expanded Thermoplastic
Microspheres”.
20
Applicants: MICROSPHERES (INDIA)
25
Address: Metoda G.I.D.C., Plot No. E-8, Taluka: Lodhika,
30 Rajkot - 360 021, Gujarat, India
35
Nationality: An Indian Company
40
45
The following specification describes the nature of the
invention and the manner in which is it is to be performed:
Page 2 of 24
5 FIELD OF THE INVENTION
The present invention relates to an expansion device (100) for preparing
hybrid filler consists of expanded hollow thermoplastic microspheres.
More particularly, the present invention relates to a device (100) for
preparing hybrid filler consisting of expanded hollow thermoplastic
10 microspheres having true density between 90 kg/m3 to 100 kg/m3 from
pre-mixed unexpanded expandable hollow thermoplastic microspheres
with fillers in which finely divided fillers can be uniformly coated on
expanded hollow thermoplastic microspheres.
The invention also relates to a method of preparing hybrid filler consists
15 of expanded thermoplastic microspheres from pre-mixed unexpanded
expandable hollow thermoplastic microspheres with fillers, by heating
thermally expandable unexpanded thermoplastic microspheres into an
expansion device of the present invention.
20 BACKGROUND OF THE INVENTION
Expandable thermoplastic microspheres are microscopic spheres
comprising a thermoplastic shell encapsulating a low boiling point
liquid hydrocarbon. When heated to a temperature high enough to
soften the thermoplastic shell, the increasing pressure of the
25 hydrocarbon will cause the microspheres to expand. When the heat is
removed microspheres remains in its new expanded form with gas
entrapped in a closed and elastic cell structure. The volume can
increase by 40 to 80 times depending upon the grades.
True density of expanded thermoplastic microspheres is around 25
30 kg/m3 and used as lightweight fillers in various applications such as
cultured marble, body fillers, polyurethanes, paint, thermosetting
materials, cable jelly and many more.
However, extremely low true density creates dusting of expanded
35 thermoplastic microspheres during production as well as during
handling at the end users.
Page 3 of 24
5 Processes or methods for expansion of thermoplastic microspheres are
described in number of patent references, some of them are explained
as under:
US4722943 dated 19/03/1987 filed by Pierce and Stevens Inc has
disclosed a process for producing free-flowing dry beads by drying
10 expandable micro spheres in the form of a wet cake, which comprises a
step of admixing a wet cake of expandable thermoplastic polymer micro
spheres (unexpanded material) with a processing aid which is a freeflowing
particulate of fibrous solid having a softening or melting
temperature higher than that of said expandable micro spheres; a step
15 of continuously drying wet cake under the temperature and time
conditions sufficient to thoroughly remove the water from the cake to
prepare free-flowing granules each having a deposition of coating layer
of said processing aid on its surface; and, a step of recovering the freeflowing
dry granules.
20 This process involves a treatment with said processing aid in the stage
of drying expandable thermoplastic polymer microspheres (unexpanded
material) in the form of wet cake. While it might be suited to large-scale
production, the process has the disadvantage of comparatively high
costs of production.
25
US5484815A dated 28/03/1994 filed by Casco Nobel AB relates to a
method for producing expanded thermoplastic microspheres by
heating. Unexpanded microspheres are dried under agitation to a dry
solids content exceeding 98% by weight, preferably 99% by weight,
30 before heating. The dried microspheres can be rewetted and then
expanded by heating. The microspheres thus produced contain but
minor amounts of agglomerates, The invention also comprises an
apparatus for expanding the dried spheres. The apparatus has a belt
conveyor (A), a device (B) for IR heating, a dosing device (C) for
35 unexpanded spheres, and a collecting device (D) for expanded spheres.
This method needs very long belt and lots of space and hence not suited
to large-scale production, as it creates lots of dusting due to its endless
Page 4 of 24
5 conveyer belt. Particles of expanded polymer microspheres
continuously flies off during production, and while transferring to silo
for packaging due to its extremely low true density of around 25 kg/m3.
US6225361B1 dated 06/04/2000 filed jointly by Japan Fillite Co Ltd
10 and Akzo Nobel NV, the said patent describes the invention and
provides expanded hollow micro sphere composite beads and a process
for producing the beads. According to the invention, finely divided
calcium carbonate can be uniformly deposited on expanded hollow
thermoplastic polymer micro spheres by a simple procedure without
15 incurring breakage of the expanded micro spheres so that the scattering
of beads can be effectively inhibited. The preferred production process
comprises admixing expanded hollow thermoplastic polymer micro
spheres (A), with colloidal calcium carbonate (B) which has been
surface-activated with a surface-treating agent or dispersing agent, e.g.
20 a fatty acid series or polymer acid series compound. The admixing can
be typically effected by dry-blending, preferably at a temperature of
about 50-100° C.
According to the process, calcium carbonate can be uniformly deposited
on pre-expanded hollow thermoplastic polymer microspheres, but do
25 not provide a method to expand unexpanded hollow thermoplastic
polymer microspheres. Such methods are not suited to large-scale
production, as it involves handling of pre-expanded hollow
thermoplastic polymer microspheres which is difficult to handle due to
its extremely low true density of around 25 kg/m3.
30
US7192989B2 dated 17/12/2003 filed by Akzo Nobel NV relates to a
method of preparing expanded thermoplastic microspheres, comprising
charging thermally expandable microspheres into an expansion device
comprising rotating feeding means enveloped by a hollow body, and one
35 or more scrapers. The invention further relates to an expansion device
for expanding thermoplastic microspheres. According to the invention,
the method comprises charging thermally expandable microspheres
into an expansion device comprising rotating feeding means enveloped
Page 5 of 24
5 by a hollow body, and one or more scrapers, wherein the scrapers
prevent layers of microspheres being built-up in the expansion device,
transporting the microspheres through the expansion device while
increasing the temperature of the microspheres to achieve expansion
thereof, and discharging the microspheres. The one or more scrapers
10 are suitably positioned between the outer radius of the feeding means
and the inner surface of the hollow body. The resulting feeding direction
in the expansion device is suitably substantially perpendicular to the
rotational movement of the feeding means.
This process is simple and allows for a continuous production of
15 expanded thermoplastic microspheres and also suited for a large-scale
production. But this process is very costly as it involves rotating feeding
means of screw-type or paddle-type and scrappers, and maintenance
cost is high due to wear and tear of rotating parts.
20 US20110178197A1 dated 30/03/2011 filed by Henkel Corp describes
a process Hollow thermoplastic microspheres may be rendered nonflammable
by coating with one or more flame retardants, while
maintaining a composite density of not greater than 0.05 g/cm3.
25 It is observed that existing processes or methods for expansion of
thermoplastic microspheres are either not suitable for large-scale
production or has high cost of production or high cost of maintenance
or require lots of space or creates lots of dusting of expanded
thermoplastic microspheres during production as well as during
30 handling at the end users due to its extremely low true density of
around 25 kg/m3.
Also currently available expanded thermoplastic microspheres are
classified as hazardous material or dangerous goods for transportation
35 purposes as per UN Combustible Solid of UN Class 4, Division 4.1. Such
cargo needs approved packaging and attracts higher fright costs.
Page 6 of 24
5 Accordingly, there was a need to develop a process which is simple and
economical, and also drastically reduce the problem of dusting of
expanded thermoplastic microspheres, both during production as well
as during handling at the end users. And also classified as nonhazardous
or non-dangerous goods for transportation purposes
10 resulting in lower freight and packaging costs.
OBJECTS OF THE PRESENT INVENTION
Accordingly, the main object of the present invention is to overcome the
problems faced by the prior art process and devices.
15 It is an object to provide an expansion device for preparing hybrid filler
consisting of expanded hollow thermoplastic microspheres from premixed
unexpanded expandable hollow thermoplastic microspheres with
fillers.
It is also to provide an expansion device for preparing hybrid filler
20 consisting of expanded hollow thermoplastic microspheres having its
true density between 90 to 100 kg/m3.
Yet there is an object to provide cost-effective, easy to use, commercially
viable device for preparing hybrid filler consisting of expanded hollow
thermoplastic microspheres from pre-mixed unexpanded expandable
25 hollow thermoplastic microspheres.
It is an object to provide a process for preparing hybrid filler consisting
of expanded hollow thermoplastic microspheres using the expansion
device of the present invention wherein the true density of obtained
hybrid filler consisting of expanded hollow thermoplastic microspheres
30 is between 90 to 100 kg/m3.
It is also an object to provide a process for preparing non-hazardous
and non-polluting hybrid filler consisting of expanded hollow
thermoplastic microspheres from pre-mixed unexpanded expandable
hollow thermoplastic microspheres.
35
Page 7 of 24
5 BRIEF DESCRIPTION OF DRAWINGS
Figure 1 shows an embodiment of the present invention.
Figure-2 shows Tray feeder 1 (105)
Figure-3 shows Tray feeder 2 (106)
Figure-4 shows openable enclosure of Tray feeder 2 (106)
10 Figure-5 shows ceramic flat heater (107)
Figure-6 shows SEM image of pre-mixed Unexpanded expandable
hollow thermoplastic microspheres with filler (CaCO3)-Batch:MICA-F-
115 of example-1 (Raw material).
Figure-7 shows SEM image of Hybrid filler (CaCO3) consist of Expanded
15 hollow thermoplastic microspheres with filler (CaCO3)-Batch:MICA-F-
115 of example-1 (Finished product).
DETAILED DESCRIPTION OF THE INVENTION
To solve above problems, inventors have developed a method and an
20 expansion device for preparing hybrid filler consisting of expanded
hollow thermoplastic microspheres from pre-mixed unexpanded
expandable hollow thermoplastic microspheres with fillers, which is
explained further as follows.
The present invention relates to an expansion device (100) for preparing
25 hybrid filler consists of expanded hollow thermoplastic microspheres.
More particularly, the present invention relates to an expansion device
(100) for preparing hybrid filler consisting of expanded hollow
thermoplastic microspheres having true density between 90 kg/m3 to
100 kg/m3 from pre-mixed unexpanded expandable hollow
30 thermoplastic microspheres with fillers (101) in which finely divided
fillers can be uniformly coated on expanded hollow thermoplastic
microspheres.
The invention also relates to a method of preparing hybrid filler
consisting of expanded hollow thermoplastic microspheres from pre35
mixed unexpanded expandable hollow thermoplastic microspheres with
fillers, by heating thermally expandable unexpanded thermoplastic
microspheres into an expansion device of the present invention.
Page 8 of 24
5 A method and an expansion device (100) for preparation of a hybrid
filler consists of expanded thermoplastic microspheres of the present
invention is surprisingly very simple and very economical as it do not
involve any expensive equipment due to its simple process. The
expansion device (100) and a process of the present invention mainly
10 comprises enclosed tray, fitted with heaters, vibrating motor and
springs, and stand fitted with adjustments to keep the enclosed tray at
a suitable decline to facilitate the movement of microspheres towards
outlet at desired speed, which makes it possible to control the duration
of the time to which unexpanded thermoplastic microspheres coated
15 with suitable filler is exposed to the required heat.
Figure 1 shows an embodiment of an expansion device (100) for
preparation of hybrid filler consists of expanded hollow thermoplastic
microspheres from pre-mixed unexpanded expandable hollow
20 thermoplastic microspheres with fillers (101), the said expansion device
(100) comprises:
Hopper (103) for storage of pre-mixed unexpanded expandable hollow
thermoplastic microspheres with fillers (101) and to ensure smooth
transfer of pre-mixed unexpanded expandable hollow thermoplastic
25 microspheres with fillers towards Spring feeder (104),
Spring feeder (104) for enabling controlled and continuous feeding of
pre-mixed unexpanded expandable hollow thermoplastic microspheres
with fillers (101) to Tray feeder 1 (105),
Tray feeder 1 (105) equipped with ceramic flat heater (107) as means for
30 heating at its bottom, the said tray feeder 1 (105) is provided to receive
pre-mixed unexpanded expandable hollow thermoplastic microspheres
(101) from spring feeder (104) and initiate the expansion of pre-mixed
unexpanded expandable hollow thermoplastic microspheres with fillers
(101) by providing heat to the unexpanded microspheres,
35 Tray feeder 2 (106) is an enclosure equipped with ceramic flat heater
(107) as means for heating at its bottom, the said enclosure (106) is
Page 9 of 24
5 provided to further soften the shell of the unexpanded hollow
thermoplastic microspheres received from tray feeder 1 (105),
Vibrating motor (108) fitted at the bottom of tray feeder 2 (106) to
provide vibration to the tray feeder 2 (106),
Vibrating spring (109) fitted at the bottom of tray feeder 2 (106) for
10 facilitating continuous and controlled vibration throughout the tray
feeder 2 (106) and to ensure smooth movement of the expanded hollow
thermoplastic microspheres towards the outlet (111);
Height adjustable stand (110) installed on the stands of the tray feeder
2 enclosure (106), to keep the tray feeder 2 (106) at a required height
15 and to maintain a suitable decline of tray feeder 2 (106) so as to control
the duration of time to which microsphere is exposed to the required
heat;
Outlet (111) to receive expanded hollow thermoplastic microspheres
coated with filler as finished product and transferring the same to silos
20 for storage and packaging.
The product received at the outlet (111) is known as hybrid filler consist
of expanded hollow thermoplastic microspheres, the true density of
hybrid filler consists of expanded hollow thermoplastic microspheres is
25 between 90 kg/m3 to 100 kg/m3.
Now, in view of figures 1 to 5, the embodiments of an expansion device
may be described as follows:
Hopper (103) for storage of raw materials:
30 Pre-mixed unexpanded expandable hollow thermoplastic microspheres
with fillers i.e. Raw Material (101) is transferred to Hopper (103) using
diaphragm pump (102). Hopper (103) is fitted with the vibrating motor
(108) to prevent raw material (101) from sticking to the inside walls of
the Hopper (103) and to ensure smooth transfer of Raw Material (101)
35 towards Spring Feeder (104).
Spring Feeder (104):
From Hopper (103), Raw Material (101) is transferred to Tray Feeder 1
(105) via Spring Feeder (104). Spring Feeder (104) breaks down small
Page 10 of 24
5 lumps, if any, of the Raw Material powder (101). Spring Feeder (104)
also enables controlled and continuous feeding of the Raw Material to
Tray Feeder 1 (105).
It is important that free flowing and lumps free powder is transferred to
Tray Feeder 1 (105) otherwise lumps will create accumulation and
10 agglomeration in Tray Feeder 2 (106) and microspheres will collapse,
and desired expansion or density of expanded thermoplastic
microspheres coated with fillers cannot be achieved. Spring feeder (104)
helps in transferring lumps free and free flowing powder to tray feeder
1 (105).
15 Tray Feeder 1 (105): Referring figures 1, 2 & 5:
Raw Material (101) transferred from Spring Feeder (104) is evenly
distributed and spread in Tray Feeder 1 (105), and further transferred
to Tray Feeder 2 (106). Tray Feeder 1 (105) is fitted with ceramic flat
heater (107) at the bottom to soften the shell of the unexpanded
20 expandable hollow thermoplastic microspheres, and initiate the
expansion, which will continue to expand and achieve full expansion in
Tray Feeder 2 (106).
It is important that Raw Material (101) is distributed and spread evenly
in Tray Feeder 1 (105) otherwise it will lead to accumulation and
25 agglomeration in Tray Feeder 2 and microspheres will collapse, and
desired expansion or density of expanded thermoplastic microspheres
coated with fillers cannot be achieved. Tray feeder 1 (105) helps in
avoiding accumulation and agglomeration of microspheres by spreading
microspheres evenly while transferring it to tray feeder 2 (106).
30 Tray Feeder 2 (106): Referring figures 1, 3, 4 & 5:
Tray Feeder 2 (106) is enclosed tray, fitted with following items:
-Ceramic flat heater (107) at the bottom to provide required heat to
the Raw Material. And outer insulation (not shown in figures) to keep
the heat inside the Tray Feeder 2 (106).
35 - Vibrating Motor (108) at the bottom to provide required vibration to
the Tray Feeder 2 (106), to facilitate further movement of the Raw
Material towards the outlet (111), and prevent accumulation of the Raw
Page 11 of 24
5 Material powder. Vibrating movement of the Tray Feeder 2 (106) also
keeps each powder particle separate during heating and expansion of
the Raw Material powder preventing agglomeration.
- Vibrating Spring (109) facilitates continuous and controlled vibration
throughout the Tray Feeder 2 (106) ensuring smooth movement of the
10 Raw Material towards the outlet (111).
- Height Adjustable Stand (110) installed on the stand of the tray feeder
2 enclosure (106) makes it possible to keep the Tray Feeder 2 (106) as
per the required decline. More the decline faster the movement of the
Raw Material in the Tray Feeder 2 (106) towards the outlet (111). This
15 makes it possible to control the duration of time to which Raw Material
is exposed to the required heat.
Tray Feeder 2 (106) is an essential part of the entire expansion device
(100) and a process to achieve desired results. Desired expansion of the
20 unexpanded thermoplastic microspheres takes place in tray feeder 2
(106). Tray Feeder 2 (106) is supported by ceramic flat heater (107),
Spring Feeder (104), Tray Feeder 1 (105), Vibrating Motor (108),
Vibrating Spring (109) and Height Adjustable Stand (110). Each of these
parts must function unanimously to achieve desired expansion or
25 density of expanded thermoplastic microspheres coated with fillers.
Further, inside or outside of the enclosure of tray feeder 1 (105) or tray
feeder 2 (106), insulation or coating may be provided to keep the heat
inside the expansion device (100), generated by ceramic flat heater
(107). There have been one or more ceramic flat heater(s) (107) may be
30 installed under the tray feeder 1 (105) or 2 (106).
Vibrating Motor (108):
Vibrating Motor (108) is fitted at the bottom of the Tray Feeder 2 (106)
to provide required vibration to the Tray Feeder 2 (106), to facilitate
further movement of the Raw Material towards the outlet (111), and
35 prevent accumulation of the Raw Material powder. Vibrating movement
of the Tray Feeder 2 (106) also keeps each powder particle separate
Page 12 of 24
5 during heating and expansion of the Raw Material powder preventing
agglomeration.
Without the Vibrating Motor (108) movement of the Raw Material
towards the outlet (111) is not possible, and desired expansion or
density of expanded thermoplastic microspheres coated with fillers
10 cannot be achieved.
Vibrating Spring (109):
Vibrating Spring (109) facilitates continuous and controlled vibration
throughout the Tray Feeder 2 (106) ensuring smooth movement of the
Raw Material towards the outlet (111).
15 Without the Vibrating Springs (109) continuous and controlled
vibration throughout the Tray Feeder 2 (106) is not possible, and
desired expansion or density of expanded thermoplastic microspheres
coated with fillers cannot be achieved.
Height Adjustable Stand (110):
20 Height Adjustable Stand (110) installed on the stand of the tray feeder
2 enclosure (106) makes it possible to keep the Tray Feeder 2 (106) as
per the required decline. More the decline faster the movement of the
Raw Material in the Tray Feeder 2 (106) towards the outlet (111). This
makes it possible to control the duration of time to which Raw Material
25 is exposed to the required heat.
Without the Height Adjustable Stand (110), it is not possible to control
the duration of time to which Raw Material is exposed to the required
heat and to achieve desired expansion or density of expanded
thermoplastic microspheres coated with fillers.
30 Outlet (111):
The Finished Product is transferred from Outlet (111) to silos for storage
and packaging (113) using diaphragm pump (112). The Finished
Product means Expanded Hollow Thermoplastic Microspheres Coated
with suitable fillers also known as Hybrid filler consist of expandable
35 hollow thermoplastic microspheres.
Control Panel (114): using main switch, It controls following functions
of the machine.
Page 13 of 24
Vibrating Motor (108) fixed to hopper (5 103): To start, stop and control
the vibration frequency of the Vibrating Motor (108) in Hopper (103).
Vibration prevents the Raw Material from sticking to the inside walls of
the Hopper and enables smooth flow of Raw Material from Spring Feeder
(104) towards Tray Feeder 1 (105).
10 Vibrating Motor (108) at the bottom tray feeder 2 (106): To start, stop
and control the vibration frequency of the Vibrating Motor (108) which
is fitted at the bottom of the Tray Feeder 2 (106) to provide required
vibration to the Tray Feeder 2 (106), to facilitate further movement of
the Raw Material towards the outlet (111), and prevent accumulation of
15 the Raw Material powder. Vibrating movement of the Tray Feeder 2
(106) also keeps each powder particle separate during heating and
expansion of the Raw Material powder preventing agglomeration.
Speed of spring feeder (104): To start, stop and control the rotation
speed (RPM) of the spring feeder (104), to control the feeding rate of the
20 Raw Material from spring feeder (104) towards Tray Feeder 1 (105).
Ceramic flat heater(s) (107) of tray feeder 1 (105): To start, stop and
control the temperature of Ceramic Flat Heaters (107) fitted at the
bottom of the Tray Feeder 1 (105). At suitable temperature shell of the
unexpanded expandable hollow thermoplastic microspheres softens,
25 and expansion is initiated, which will continue to expand and achieve
full expansion in Tray Feeder 2 (106).
Ceramic flat heater(s) (107) of tray feeder 2 (106): To start, stop and
control the temperature of Ceramic Flat Heaters (107) fitted at the
bottom of the Tray Feeder 2 (106). These Heaters (107) provide required
30 heat to the Raw Material. And outer insulation to keep the heat inside
the Tray Feeder 2 (106).
Pre-mix of unexpanded expandable hollow thermoplastic microspheres
with fillers (101) includes (i) mixture of unexpanded expandable hollow
35 thermoplastic microspheres and (ii) suitable Fillers.
Unexpanded expandable hollow thermoplastic microspheres for premixing
purpose with suitable filler are selected from microspheres
Page 14 of 24
5 having a thermoplastic shell made from polymers or co-polymers
obtainable by polymerizing various ethylenically unsaturated
monomers which can be nitrite containing monomers such as acrylo
nitrile, methacrylo nitrile, α-chloroacrylo nitrile, α-ethoxyacrylo nitrile,
fumaro nitrile, croto nitrile, acrylic esters such as methylacrylate or
10 ethyl acrylate, methacrylic esters such as methyl methacrylate,
isobornyl methacrylate or ethyl methacrylate, vinyl halides such as
vinyl chloride, vinylidene halides such as vinylidene chloride, vinyl
pyridine, vinyl esters such as vinyl acetate, styrenes such as styrene,
halogenated styrenes or α-methyl styrene, or dienes such as butadiene,
15 isoprene and chloroprene. Any mixtures of the abovementioned
monomers may also be used. It may sometimes be desirable that the
monomers for the polymer shell also comprise crosslinking
multifunctional monomers, such as one or more of divinyl benzene,
ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate,
20 triethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate,
1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate,
glycerol di(meth)acrylate, 1,3-butanediol di(meth)acrylate, neopentyl
glycol di(meth)acrylate, 1,10-decanediol di(meth)acrylate,
pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate,
25 pentaerythritol hexa(meth)acrylate, dimethylol tricyclodecane
di(meth)acrylate, triallylformal tri(meth)acrylate, allyl methacrylate,
trimethylol propane tri(meth)acrylate, trimethylol propane triacrylate,
tributanediol di(meth)acrylate, PEG-200 di(meth)acrylate, PEG-400
di(meth)acrylate, PEG-600 di(meth)acrylate, 3-acryloyloxyglycol
30 monoacrylate, triacryl formal or triallyl isocyanate, triallyl isocyanurate
etc. If present, such crosslinking monomers preferably constitute from
about 0.1 to about 1 wt %, most preferably from about 0.2 to about 0.5
wt % of the total amounts of monomers for the polymer shell. Preferably
the polymer shell constitutes from about 60 to about 95 wt %, most
35 preferably from about 75 to about 85 wt % of the total microsphere.
Page 15 of 24
5 Further, unexpanded expandable hollow thermoplastic microspheres
comprise propellant. The propellant in a microsphere is normally a
liquid having a boiling temperature not higher than the softening
temperature of the thermoplastic polymer shell. The propellant, also
called the blowing agent or foaming agent, can be hydrocarbons such
10 as n-pentane, isopentane, neopentane, butane, isobutane, hexane,
isohexane, neohexane, heptane, isoheptane, octane and isooctane, or
mixtures thereof. Also, other hydrocarbon types can also be used, such
as petroleum ether, and chlorinated or fluorinated hydrocarbons, such
as methyl chloride, methylene chloride, dichloro ethane, dichloro
15 ethylene, trichloro ethane, trichloro ethylene, trichlorofluoro methane
etc. The propellant suitably makes up from about 5 to about 40 weight
% of the microsphere.
The suitable fillers are in the form of fine particles having a particle
20 diameter range from about 1 to 15 microns. Examples of fillers are but
not limited to calcium carbonate, calcium phosphates, calcium
sulphate, talc, dolomite, kaolin, titanium oxide, silicon oxides, iron
oxides, aluminium oxides and hydroxides, zinc oxide, magnesium
carbonate, magnesium phosphates, magnesium hydroxide,
25 hydrotalcite, mica, barytes, pearlites, vermiculites, hollow quartz,
ceramic spheres, glass spheres or combinations of different fillers.
Fillers may be used in its pure form like precipitated calcium carbonate
or precipitated silica available commercially or it may be surface
treated.
30
For pre-mixing purpose, filler/s are mixed with thermally unexpanded
expandable hollow thermoplastic microspheres in the required ratio as
per the suitability. This weight ratio for combination ranges from the
combination of 1% of microspheres and 99% filler/s to combination of
35 99% of microspheres and 1% filler/s, and in any ratios in between these
ratios, as per the suitability. Preferably in the combination of 10-20%
of microspheres and 80-90% filler/s.
Page 16 of 24
5 A hybrid filler consists of expanded thermoplastic microspheres are
discharged through an outlet (111) and suitably pumped away using
diaphragm pump (112). Tray feeder-2 (106) is height adjustable (110)
to keep the tray (106) at suitable decline to control the time the
thermally expandable thermoplastic microspheres remain in tray and
10 in heat.
A method of the present invention allows for a continuous production,
and provides very good control over the expansion process, to achieve
desired expansion or density of expanded thermoplastic microspheres
15 coated with suitable filler. The parts involved are inexpensive, and as
there are very few parts involved it is very economical to maintain as
well.
In the process of the present invention, approx.. 15% of unexpanded
20 thermoplastic microspheres are coated with approx.. 85% of suitable
filler such as Calcium Carbonate. Such hybrid filler i.e. coated
expanded thermoplastic microspheres maintains the Functional
Properties of expanded thermoplastic microspheres, and also
drastically reduces the problem of dusting of expanded thermoplastic
25 microspheres both during production as well as during handling at the
end users.
As approx.. 85% of such hybrid filler i.e. coated expanded thermoplastic
microspheres consist of heavy filler such as Calcium Carbonate,
resulting density is around 100 kg/m3, preferably density is between 90
30 to 100 kg/m3. Due to higher density of such hybrid filler of around 100
kg/m3, in comparison with around 25 kg/m3 density of expanded
thermoplastic microspheres, it is easier to handle and drastically
reduces the dusting both during production as well as during handling
at the end users. Such hybrid filler i.e. coated expanded thermoplastic
35 microspheres improves the working environment and drastically
reduces the human health hazards.
The thermally expandable thermoplastic microspheres used in the
present invention starts to expand between at around 25°C. Preferably
Page 17 of 24
5 100°C to 140°C. The thermally expandable thermoplastic microspheres
used in the present invention achieves full expansion between at
around 100°C to 310°C depending upon the grades. Preferably 140°C
to 180°C. The volume of thermally expandable thermoplastic
microspheres can increase by 40 to 80 times depending upon the
10 grades.
Expandable thermoplastic microspheres comprise a thermoplastic shell
encapsulating a low boiling point liquid hydrocarbon. When heated to
a temperature high enough to soften the thermoplastic shell, the
increasing pressure of the hydrocarbon will cause the microspheres to
15 expand. When the heat is removed microspheres remains in its new
expanded form with gas entrapped in a closed and elastic cell structure.
The volume can increase by 40 to 80 times depending upon the grades.
Thus it is possible to achieve the desired density of thermally expanded
thermoplastic microspheres coated with fillers by using a combination
20 of heating temperature and the time of heating in the expansion device
of the present invention. Expandable thermoplastic microspheres can
survive lower temperature for longer time, and can survive higher
temperature for shorter time.
EXAMPLES OF THE PRESENT INVENTION
25 An expansion device (100) comprising a closed body according to the
present invention having a tray as feeding means is used for expanding
thermoplastic expandable microspheres pre-mixed with suitable
filler/s. The tray is 1850 mm long and 450 mm wide. Expandable
thermoplastic microspheres pre-mixed with suitable filler/s, at suitable
30 ratio, is heated into the expansion device at a suitable temperature, for
a suitable time.
Approx. 15% Unexpanded Microspheres are pre-mixed with approx..
85% of precipitated Calcium Carbonate (CaCO3) in a Ribbon Blender for
about 3 hours to get homogenous mixture. Such mixture coats the
35 unexpanded expandable hollow thermoplastic microspheres with
CaCO3 and hence expanded hollow thermoplastic microspheres
Page 18 of 24
remains easi 5 ly flowable in Expansion Unit and do not get agglomerated.
Different fillers can be used in different ratios as per the requirement.
Some of the examples with different ratios of unexpanded expandable
microspheres and fillers have been provided as follows:
With precipitated Calcium carbonate (CaCO3) as filler:
Sr.
No.
Name of
the
Product
Unexpanded
Thermoplastic
Microspheres
Content (%)
Precipitated
Calcium
Carbonate
Content (%)
True
Density
(kg/m3)
Temperature
(Deg. C)
1 MICAF115
15 85 100 160
2 MICAF115
50 50 35.8 160
3 MICAF115
85 15 24 160
10
With precipitated silica as filler:
Sr.
No.
Name of
the
Product
Unexpanded
Thermoplastic
Microspheres
Content (%)
Precipitated
Silica Content
(%)
True
Density
(kg/m3)
Temperature
(Deg. C)
1 MISIF115
15 85 96.9 160
2 MISIF115
50 50 34 160
3 MISIF115
85 15 25.6 160
RESULTS: REFERRING TO FIGURES 6 & 7:
SEM images taken at SICART (Sophisticated Instrumentation Centre for
15 Applied Research and Testing), Vallabh Vidyanagar, Gujarat confirms
that the experimental grade MICA-F115 is expanded as desired. MICAF115
is combination of approx.. 15% of hollow thermoplastic
microspheres and approx.. 85% of Calcium Carbonate. MICA-F115 has
true density of 100 kg/m3.
20
According to the test conducted at Sigma-HSE, UK such hybrid filler
i.e. coated expanded thermoplastic microspheres consist of heavy filler
such as Calcium Carbonate, should not be regulated or classified for
transportation purposes as a hazardous material or a dangerous good.
Page 19 of 24
5 Also, under Classification, Labelling and Packaging (CLP) the material
would not be considered hazardous.
ADVANTAGES OF THE PRESENT INVENTION
Now, without limiting the scope of the present invention, advantages
10 can be described as follows:
1. Expanded thermoplastic microspheres of the present invention are
easier to handle than currently available expanded thermoplastic
microspheres. This is due to higher true density of around 100
kg/m3 of coated expanded thermoplastic microspheres in
15 comparison with true density of around 25 kg/m3 expanded
thermoplastic microspheres.
2. According to the test conducted at Sigma-HSE-UK, expanded
microspheres of examples provided herein the present invention
should not be regulated or classified for transportation purposes as
20 a hazardous material or a dangerous good. Also, under
Classification, Labelling and Packaging (CLP) the material would not
be considered hazardous. Whereas currently available expanded
thermoplastic microspheres having true density of around 25 kg/m3
expanded thermoplastic microspheres are regulated and classified
25 for transportation purposes as a hazardous material or a dangerous
good. Also, under Classification, Labelling and Packaging (CLP) the
material are considered hazardous.
List of Parts mentioned in Figure 1 of the present invention
30 101) Pre-mixed microspheres with fillers i.e. Raw material.
102) Diaphragm Pump
103) Hopper
104) Spring Feeder
105) Tray Feeder 1
35 106) Tray Feeder 2
107) Heated Tray (Ceramic flat heater)
108) Vibrating Motor
Page 20 of 24
5 109) Vibrating Spring
110) Height Adjustable Stand
111) Outlet
112) Diaphragm Pump
113) To Silo or Packing Station
10 114) Control Panel
Page 21 of 24
5 We claim:
1. An expansion device (100) for preparation of a Hybrid Filler
consists of expanded thermoplastic microspheres from pre-mixed
unexpanded expandable hollow thermoplastic microspheres with
fillers (101), the said expansion device (100) comprises:
10 Hopper (103) for storage of pre-mixed unexpanded expandable
hollow thermoplastic microspheres with fillers (101) and to
ensure smooth transfer of pre-mixed unexpanded expandable
hollow thermoplastic microspheres with fillers towards Spring
feeder (104) using diaphragm pump (102);
15 Spring feeder (104) for enabling controlled and continuous
feeding of pre-mixed unexpanded expandable hollow
thermoplastic microspheres with fillers to Tray feeder 1 (105),
Tray feeder 1 (105) equipped with at least one ceramic flat heater
(107) at its bottom, the said tray feeder 1 (105) receive pre-mixed
20 unexpanded expandable hollow thermoplastic microspheres with
fillers (101) from spring feeder (104) and to initiate the expansion
of unexpanded expandable hollow thermoplastic microspheres
with fillers (101) by providing heat to the unexpanded
microspheres,
25 Tray feeder 2 (106) is an enclosure equipped with at least one
ceramic flat heater (107) at its bottom, the said enclosure (106) is
provided to further soften the shell of the unexpanded hollow
thermoplastic microspheres received from tray feeder 1 (105),
Vibrating motor (108) fitted at the bottom of tray feeder 2 (106) to
30 provide vibration to the tray feeder 2 (106),
Vibrating spring (109) fitted at the bottom of tray feeder 2 (106)
for facilitating continuous and controlled vibration throughout
the tray feeder 2 (106) and to ensure smooth movement of the
expanded hollow thermoplastic microspheres towards the outlet
35 (111);
Height adjustable stand (110) installed on the stands of the tray
feeder 2 enclosure (106), to keep the tray feeder 2 (106) at a
Page 22 of 24
required height and to maintain a suitable 5 decline of tray feeder
2 (106) so as to control the duration of time to which microsphere
is exposed to the required heat.
Outlet (111) to receive expanded hollow thermoplastic
microspheres coated with filler as finished product and
10 transferring the same to silos for storage and packaging (113)
using diaphragm pump (112).
2. A method for preparation of hybrid filler consists of expanded
thermoplastic microspheres having true density between 90
kg/m3 to 100 kg/m3 from pre-mixed unexpanded expandable
15 hollow thermoplastic microspheres with fillers, the said method
comprises the steps of:
transferring at a continuous rate, the pre-mixed unexpanded
expandable hollow microspheres with filler to tray feeder 1 from
hopper using spring feeder and heated at a temperature between
20 500C to 1000C enabling expansion of pre-mixed microspheres
with fillers,
Continuously passing it from tray feeder 1 to tray feeder 2 at a
temperature between 1300C to 1800C by maintaining desired
height of tray feeder 2 so as to keep tray feeder 2 at a suitable
25 decline and constantly providing vibration to tray feeder 2
enclosure in order to prevent accumulation of thermoplastic
microspheres in the expansion device,
Receiving hybrid filler consists of expanded thermoplastic
microspheres having true density between 90kg/m3 to 100 kg/m3
30 from tray feeder 2 into the outlet,
Sending it to silos for storage and packaging purpose.
3. A method as claimed in claim-2 wherein the weight ratio of
microspheres to fillers in pre-mixed expandable unexpanded
microspheres with filler is between 10-20% microspheres to 80-
35 90% fillers.
4. A method as claimed in claim-2 wherein vibration is provided
using one or more vibrating motor installed under tray feeder 2.
Page 23 of 24
5 5. A method as claimed in claim-2 wherein unexpanded expandable
hollow thermoplastic microspheres for pre-mixing purpose with
suitable filler are selected from microspheres having a
thermoplastic shell made from polymers or co-polymers
obtainable by polymerizing various ethylenically unsaturated
10 monomers which can be nitrite containing monomers such as
acrylo nitrile, methacrylo nitrile, α-chloroacrylo nitrile, α-
ethoxyacrylo nitrile, fumaro nitrile, croto nitrile, acrylic esters
such as methylacrylate or ethyl acrylate, methacrylic esters such
as methyl methacrylate, isobornyl methacrylate or ethyl
15 methacrylate, vinyl halides such as vinyl chloride, vinylidene
halides such as vinylidene chloride, vinyl pyridine, vinyl esters
such as vinyl acetate, styrenes such as styrene, halogenated
styrenes or α-methyl styrene, or dienes such as butadiene,
isoprene and chloroprene. Any mixtures of the above mentioned
20 monomers may also be used. It may sometimes be desirable that
the monomers for the polymer shell also comprise crosslinking
multifunctional monomers, such as one or more of divinyl
benzene, ethylene glycol di(meth)acrylate, diethylene glycol
di(meth)acrylate, triethylene glycol di(meth)acrylate, propylene
25 glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-
hexanediol di(meth)acrylate, glycerol di(meth)acrylate, 1,3-
butanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate,
1,10-decanediol di(meth)acrylate, pentaerythritol
tri(meth)acrylate, pentaerythritol tetra(meth)acrylate,
30 pentaerythritol hexa(meth)acrylate, dimethylol tricyclodecane
di(meth)acrylate, triallylformal tri(meth)acrylate, allyl
methacrylate, trimethylol propane tri(meth)acrylate, trimethylol
propane triacrylate, tributanediol di(meth)acrylate, PEG-200
di(meth)acrylate, PEG-400 di(meth)acrylate, PEG-600
35 di(meth)acrylate, 3-acryloyloxyglycol monoacrylate, triacryl
formal or triallyl isocyanate, triallyl isocyanurate etc.
Page 24 of 24
5 6. A method as claimed in claim-2 wherein filler is selected from
calcium carbonate, calcium phosphates, calcium sulphate, talc,
dolomite, kaolin, titanium oxide, silicon oxides, iron oxides,
aluminium oxides and hydroxides, zinc oxide, magnesium
carbonate, magnesium phosphates, magnesium hydroxide,
10 hydrotalcite, mica, barytes, pearlites, vermiculites, hollow quartz,
ceramic spheres, glass spheres or combinations thereof.
7. A method as claimed in claim-2 & 6 wherein filler is selected from
precipitated calcium carbonate or precipitated silica.