Note: Descriptions are shown in the official language in which they were submitted.
2~
COATING PROCESS
This invention relates to a novel agglomeration,
coating or encapsulation process. The process has a wide
range of applications. It can be applied to coating or
encapsulating solid particles, liquid droplets or a mixture
of the two.
In a first aspect the invention provides a process
for coating or encapsulating solid particles and/or liquid
droplets, the process comprising a first step of forming a
melt of a coating material with the said particles and/or
droplets as a disperse phase therein,
and a second step of destabilizing the melt by
addition of solid particles and/or by cooling, causing the
melt to crumble to a particulate product whereof the
particles comprise the coating material with the particles
and/or droplets of the`disperse phase embedded therein.
The coating process may serve as a means of agglomeration of
disperse phase particles.
A second aspect of this invention is the
particulate products of the process.
Our European application EP-A-303416 which is not
a prior publication discloses a form of the present
invention carried out using polyalkylene or copolymers with
at least 70~ polyalkylene therein as the coating material,
while using water-insoluble inorganic abrasive material to
provide ~oth the particles which are coated and particles
which destabilize the melt.
2 X~ 4
Certain forms of the present invention therefore
do not include the combination of water-insoluble solid
particles as the sole disperse phase and polyalkylene or
alkylene copolymers with not more than 30% of other monomers
containing a carboxylic acid or ester group as the organic
polymeric material.
Essential to this invention is the finding that a
melt containing a sufficient quantity of a disperse phase
can be induced to crumble to a particulate state in which
the disperse phase is embedded in particles of what was
previously the continuous phase. Crumbling occurs when the
amount of disperse phase present exceeds the amount which
the continuous phase is able to support. It can be induced
by cooling - which reduces the abllity of the continuous
~5 phase to support disperse phase - or by direct addition of
some material which adds to the total amount of disperse
materlal. Combination of cooling and addition of solid
disperse phase is most effective since ~he solid material
causes crumbling locally and cooling fortifies this phase
separation.
The coating material which forms a melt will
generally be one or more organic compounds. It may
especially be provided by an organic polymeric material
which melts at a temperature above ambient. Another
possihility is that the coating material i~ waxy, e.g.
paraffin wax. A further possibility is that the coating
material is an organic compound which contains alkyl groups
of deterge~t chain length, i.e. 8 to 20 carbon a~oms, as in
Z~
a surfactant, soap or fatty acid.
An advantage of the present invention is that it
is effective for coating or encapsulating small particles,
and mixtures of particles displaying a range of particle
sizes. Some known coating processes, such as fluidized
beds, are least effective with small particles~
The invention can be used to coat or encapsulate a
range of materials and by doing so can serve a variety of
useful purposes depending on the nature of the encapsulated
material and the polymeric coating material.
A characteristic of the invention is that solvent
is often not employed, so that the product does not ccntain
traces of solvent.
Since the invention can be implemented in a wide
variety of ways, it is convenient to describe a
straightforward example in general terms, by way of
illustration, before proceeding with more general
discussion. This example consists in coating sodium
chloride with polyethylene glycol having an average
molecular weight of 20,000. The final product contains, by
weight:
polyethylene glycol (PEG 20,000) 25%
- sodium chloride 65
silica, mean particle size 7 x 10-9m 10~
Initially the polyethylene glycol is heated to
somèwhat above its melting point. The sodium chloride, as
fine crystals, is mixed into the molten polymer forming a
z~
disperse phase in the melt. The melt is now cooled to
slightly above the melting point of the polymer. The silica
is mixed in and the mixture allowed to cool further. The
melt crumbles into particles. These particles are mostly
agglomerates of sodium chloride crystals embedded in
solidified polymer, with silica mainly at the exterior of
these particles.
The materials in the above example are thus an
organic polymeric coating material which in the above
example was polyethylene glycol, a solid disperse phase
which was sodium chloride and a "crumbling agent" which was
silica. The term "crumbling agent" is used because it
causes the melt to crumble into particulate form.
In order that a coating material should form an
effective coating of another material, it should be
adequately compatible with it. Where this is lacking, phase
separatlon or weak, easily removed coatings result. When
appropriate, compatibility can be enhanced by any of:
(i) coating a solid disperse phase with silane or
titanate coupling agents (which are known per se)
(ii) inducing bonding between the coating material and
the disperse phase
(iii) including surfactant to form a "bridge" at the
interface between disperse phase and coating material.
Some surfactants may also be incorporated into the
coatiny material, or used as coating material. ~hen more
than ons coating is to be employed, surfactant can form a
"bridge" to enhance the compatibility of the coating
7~ 4
materials.
In the process of this invention it is not
essential that the disperse phase be solid. As an
alternative, or in addition, a liquid disperse phase may be
employed. This may be liquid at ambient temperature, or it
may be a material which is solid at ambient temperature but
is sufficiently low melting that it is liquid at the
temperatures of processing.
Further possibilities are that liquid may be
incorporated into the pores of a porous disperse phase, or
liquid may be dispersed in coating material applied to a
solid disperse phase. Indeed it would be possible for
liquid to be present in both the coating material and a
porous solid disperse phase.
The process may be put to a number of uses.
Possible applications include:-
Agglomeration of small particles into larger, more
convenient, sizes. This could serve for instance to
ameliorate dustiness or poor flow characteristics of finely
divided material.
Protective coating of a material, protecting it
from an adverse environment until the time of use. This
could for ins-tance serve to protect a chemically reactive
material until it is used.
Delayed release of a material, or controlled slow
release, due to the presence of a coating.
Conversion of a liquid into the form of a
particulate solid. This for instance would enable
6 2~ 9~
incorporation of a liquid ingredient into a particulate
solid product.
Grouping multiple materials together. This for
instance could be used to prevent segregation of materials
included in a particulate end product.
There are various developments of the basic
process which may be employed:-
A preliminary coating of a liquid may be appliedto a solid disperse phase. In particular such a preliminary
coating may be a coating of surfactant or of a li~uid which
includes a surfactant. Such a preliminary coating may serve
to provide a desired degree of compatibility with the
polymeric coating material. Another use for a preliminary
coating on the solid disperse phase is to provide a barrier
layer to isolate a potentially reactive solid disperse phase
during mising with polymer at elevated temperaturesO
Wher. a solid disperse phase is porous, a
preliminary coating of a high molecular weight polymer may
be used before coating with a lower molecular weight coating
material in order that the porous solid does not absorb
excessive quantities of the coating material.
Another development of the process is to apply
multiple coating layers. In particular, particles may be
encapsulated with a first coating material by a procedure in
accordance with the invention after which a second outer
coating may be applied either by use of a further procedure
in accordance with the invention or by means of some other
coating technique such as fluidized bed coating.
When two coatings are provided, one useful
possibility is that the inner coating provides mechanical
strength while the outer coating provides a barrier to
protect the coated material from the surrounding
environment. Another possibility is for the outer coating
to be a water-insolu~le coating (or a poorly soluble outer
coating) applied over particles which are water-soluble or
water-swellable. Such an arrangement can serve to delay
release of the encapsulated material when the particles are
placed in water until such time as the water has penetrated
the outer coating. Swelling of the inner particles when
water does penetrate to them may at that point serve to
rupture the outer coating so that after a delay caused by
the outer coating the subsequent release is not restrained
by the outer coating.
Within this general concept, one possibility is
for the inner particles (that is to say the particles to
which the second, outer coating is applied) to contain a
water-swellable crumbling agent. Another possibility is for
these particles to contain as first coating material an
organic polymeric material which is water-soluble or water-
swellable. In this latter case, the second, outer coating
can serve to delay release of any part of the encapsulated
dispersed phase until the outer coating is penetrated, after
which dissolution or swelling of the organic polymeric
material within the particles controls the rate of release
of the disperse phase.
Posslbllities for materials will now be discussed.
X~4~a~
Coating Material
One possibility for this is an organic polymer or
copolymer which is suitable for the end use of the
encapsulated disperse phase. The polymeric material needs
to melt at a temperature which is suitable for incorporating
the disperse phase. The material may be a mixture of
polymers.
If it is desired to use a polymer of high melting
point or which degrades before reaching its melting point,
then a polymer of low molecular wei~ht may be used as a
solvent for the polymer. Alternatively some organic solvent
may be used to form a viscous concentrated solution of the
polymer.
Use of high molecular weight polymer may be
advantageous in that less crumbling agent tends to be
required.
Another possibility for the coating material is
non-soap surfactant. This may, or may not, be surfactant
derived from a polymer such as fatty acyl and fatty diacyl
derivatives of polyethyleneglycol.
Another useful possibility for the coating
material is a mixture of soap and fatty acid. Yet another
possibility is waxy material such as paraffin wax with
melting point above ambient temperature.
Blends of materials may be used in order to obtain
desired properties of the coating material. These blends
may in particular be blends of two or more polymers, or
9 2~
blends of polymer(s) with non soap surfactants or with soap
and fatty acid. For instance, surfactant may serve as
solvent for high molecular weight polymer.
When the coating material is a blend of compatible
materials, the melting and crystallisation behaviour of the
components of the blend is modified. These properties of a
blend can be determined by differential scanning
calorimetry.
Blends of materials may be chosen for release of
the enclosed material to be brought about by any of:
physical corrosion of coating,
solution of coating on exposure to water,
swelling of coating on exposure to water,
permeation of water throuyh insoluble porous
coating, possibly followed by rupture on swelling of
encapsulated material,
exposure to spe$ified temperature,
exposure to specified pH.
Examples of coating materials which may be used
alone or in blends are:
1. Polyethylene glycol (PEG) and polyethylene oxide
(PE0): This system provides a very extensive range of
molecular weight ranging from a few hundreds to several
millions. PEGs can be used by themselves as coating agent
or may be used to dissolve other polymers.
Z1~4~
2. Polyvinyl pyrrolidone (PVP): Generally used in
combination with other polymers.
3. Poly (acrylic acid) (PAA): Of use in
Weak acid. systems where
5 4. Cellulose acetate phthalate release of the
(CAP): Weak acid. ~ coated material
5. Polyvinyl acetate phthalate ¦ is dependent on
(PVAP): Weak acid. J pH
6. poly (caprolactone) (PCL): poly (caprolactone)
diol, (PCL-diol).
PCL has high permeability despite the fact it is
not water soluble. May also be used to form blends with
other water soluble polymers.
7. Poly (ethylene-vinyl acetate)
copolymer (EVAC-CP).
8. Poly (ethylene-acrylic acid)
copolymer (EAA-CP).
9. Oxidised polyethylene (OPE): This polymer is
used to provide compatibility between polyalkylenes and
water-soluble polymers or to modify the release
characteristics of the other water-soluble polymers such as
PEG's and PEO's.
10. Polyethylene glycol - fatty acid esters: These
polymeric surfactants offer a wide range of melting point
and water solubility/dispersibility depending on the length
of the polyethylene glycol chain and fatty acid chain. For
11 2~
example the monolaurate of polyethylene glycol with average
molecular weight 6000 has melting point of 61C and is
highly water-soluble while the dilaurate of polyethylene
glycol with average molecular weight 400 has melting point
of 18C and is not water-soluble, merely water -
dispersible~ These materials can be used to provide two
coatings which are compatible with each other but have
different properties. PEG 6000 monolaurate can be used to
provide a mechanically strong water-soluble first coating
while PEG 400 dilaurate can be applied as a second coating
forming a vapour barrier.
~ lends of materials which have been found useful
are:
1. Soap/fatty acid/polymer, especially sodium
stearate/lauric acid/ethylene acrylic acid copolymer with a
weight ratio 0.5 to 2.0 : 0.5 to 2.0: 1.
2. Fatty alcohol ethoxylate/polymer especially when
the polymer is in lesser amount than the fatty alcohol
ethoxylate and is polycaprolactone or ethylene acrylic acid
copolymer.
In the first o these blends we have found that
the presence of the polymer leads to a lowering of melting
point, crystallinity and crystal size. It also modifies the
water solubility. In the second we have found that
inclusion of this or other polymers leads to an increase in
melting point and in the hardness of the coating material.
12 2~ 4
Solid Disperse Phase
A wide variety of materials may be employed.
Examples are sodium chloride, sodium carbonate, organic
peroxy acids and their salts (bleaching agents), tetra-
acetyl ethylene diamine (TAED, a low temperature bleachprecursor), sodium perborate (bleaching agent), sodium
dichloro isocyanurate dihydrate (SDCCA, a bleaching agent)
and distearyl dimethyl ammonium chloride (a cationic surface
active agent sold under the Trade Mark AROSURF TA-100).
Solid disperse phase particles may be porous,
organic or inorganic, and may contain a liquid entrapped in
the inter- or intra-particle pores. Examples of solid
disperse phase particles are anhydrous sodium carbonate and
porous silica. Liquids which may be carried by a porous
disperse phase include antifoam agents and perfumes.
Liquid Disperse Phase
Again a wide variety of materials can be
dispersed. Particular examples are silicone fluid (serves
as a fabric softener) and a viscous dispersion of
hydrophobed silica in silicone oil which serve as antifoam
agent.
Crumbling Agent
The function of the crumbling agent is to enhance,
locally or globally, the total amount of dispersed material
beyond the point at which the molten system becomes
13 Z0~34~
unstable. The crumbling agent has to be solid at the
temperature at which crumbling occurs and should not
dissolve in the coating material at the temperature of
processing. Subject to these constraints, a wide range of
materials can be employed. Crumbling agents may be
inorganic particulate solids, or may be particles of high
molecular weight polymer. Other organic or inorganic
particulate solids are not ruled out, but will generally be
less econo~ical and therefore are not preferred unless they
have a specific function in the final product as discussed
later. Crosslinked polymer powders and polymer latex
particles may also be considered as crumbling agent. The
effectiveness of a crumbling agent will be enhanced if its
particle size is small. Examples of crumbling agents are:
Silica, anionic or cationic clays, zeolite, talc,
sodium carbonate, sodium bicarbonate, calcite,
polyethylene oxide (PEO), sodium carboxymethyl
cellulose, starch, cellulose acetate,
microcrystalline cellulose.
The crumbling agent may be provided by a further
quantity of the material used as solid disperse phase (if
any)~
Much of the crumbling agent adheres to the surface
of the particles formed by crumbling and it can therefore be
used to modlfy the surface characteristics of these
particles. For instance the crumbling agent may confer
hydrophilic or hydrophobic character and/or reduce the
14 2~ 4
permeability of the coating to gases and vapours.
Crumbling agent in particles with a double coating
can provide some important functions. In double coated
particles most of the crumbling agent can be placed at the
exterior of the particles with a single coating, which are
formed before the application of the second coating. A
different crumbling agent (inert) can be used to induce
crumbling in the second coating step, if this step is
carried out in accordance with the invention (rather than by
using conventional coating techniques such as fluidized bed
coating).
Other possible functions of the crumbling agent in
double coat particles are summarised below:
1. Crumbling agent can absorb water, permeating
through the outer coat, thus acting as a water sink to stop
water affecting the encapsulated material during storage, or
even provide delay in the release of the solid dispersed
phase. Crumbling agents which can act as water sink are
water soluble or water swellable polymers such as sodium
carboxymethyl cellulose, clays, silica gels and inorganic
salts which re-crystallise with large amounts of crystal
water. Examples of such salts are sodium tripolyphosphate,
sodium pyrophosphate, sodium orthophosphate, sodium
polyphosphate glasses, aluminium sulphate A12(S04 )3 and
sodium carbonate.
2. In addition to the anhydrous salts referred to
above, inorganic salts such as LiI, LiBr, LiCl and AlCl3
~3~
generate large amounts of heat upon hydration. Heat
generated as a result of water absorption through the outer
coat and hydration of the crumbling agent may serve to heal
the surface cracks thus improving the storage stability of
the capsules.
3. When water-swellable materials such as modified
starches, cellulose, certain cross linked polymers or clays
are used as crumbling agents they can also act as trigger
agents to break the outer coat due to swelling of the
crumbling agent upon contact with water permeating through
voids in the outer coat.
4. Crumbling agent can also be a chemical which is to
be delivered sequentially before the main dispersed solid
phase which is encapsulated by the first coat.
Surfactants
As already mentioned, surfactants may be used as
or included in the coating material. As well as this use of
surfactants, surfactants may be included in order to
emulsify a liquid disperse phase, or to effect surface
modification of a solid dispersed phase. In emulsions
involving silicone fluid or silicone antifoam, silicone
glycol copolymer surfactants DC190, DC193 and DC198 (in
particular DC193) supplied by Dow Corning were found to be a
suitable surfactant. The surfactants DC193 and DC198 were
also then used in the polymer phase which was the coating
material. Presence of a surfactant to effect surface
modification of a solid phase may in particular be utilisPd
if the solid is not compatible with the coating material.
16 ~ 4~
Outer Coating
If an outer coating is employed, i.e. a second
coating onto previously coated particles, it may be composed
of any coating material which is immobile at ambient
temperature (or whatever temperature the final particles are
to be kept at). Paraffin wax and poly(caprolactone)diol or
poly(caprolactone)triol or their mixture are examples of
materials which may be employed as an outer coating. Water
soluble polymers such as polyethylene glycol may also be
used.
Processing Procedure
The central step of the processing is the
crumbling to particles. ~ melt of the organic polymeric
material, containing disperse phase, is induced to crumble
by cooling, addition of crumbling agent or some combination
of both, while mixing is continued.
If a liquid disperse phase is used, this is
preferably first emulsified in the coating material in a
suitable mixing apparatus able to form an emulsion. The
temperature must remain above the melting point of the
coating material and if desired the liquid disperse phase
may be preheated to above this temperature before adding to
the mixer. The li~uid disperse phase may be mixed with
surfactant before being mixed with the coating material.
In one preferred procedure the coating material
and additional surfactant (if required) are supplied to a
suitable mixer and brought to a temperature above the
Z(l~
17
melting point of the coating material.
If solid disperse phase is used, this is next
added to the mixer and mixed into the molten polymeric
material to form a homogeneous melt. This again is carried
out at a temperature above the melting point of the
polymeric material and if desired the solid disperse phase
is preheated before it is added to the mixer. (Since a
homogeneous melt is formed, a reversed order of addition to
the mixer will generally be possible, if desired).
The temperature of the mix is now reduced to just
above the melting point of the coating agent: 5C above the
melting point is suitable. The crumbling agent is next
added and the mixture is cooled further. It has been found
convenient to add around 65~ of the crumbling agent while
holding the temperature just above the melting point of the
polymeric material and then start cooling while adding the
balance of the crumbling agent. Crumbling of the melt will
generally commence before all of the crumbling agent has
been added but the further addition of crumbling agent will
complete the process and may bring about some further
crumbling to smaller sized particles. It is desirable to
continue mixing until the temperature has cooled to 30C
less than the melting point of the coating agent. The
particulate material which is produced may be subjected to a
size reduction process at this stage if smaller particles
are desired.
If the disperse phase is porous solid with liquid
absorbed therein, it may be desirable to avoid the
20~
18
generation of severe stresses during mixing, because high
stress could cause break up of the porous solid and release
of the absorbed liquid. Low rotational speed mixing is then
preferable.
It may be desirable to dose the molten coating
material onto the solid disperse phase until melt formation
commences and then start cooling and adding crumbling agent
without waiting for the melt to become homogeneous.
The process of the invention can be carried out as
a batch process, for instance using a Z-blade mixer, or as a
continuous process, for instance using a twin screw extruder
with more than one zone for introduction of material into
the extruder. In a batch process, crumbling could be
brought about in different apparatus to that used for
initial melt formation.
Examples of the invention are set out below.
Percentages and amounts are by weight unless otherwise
stated.
These Examples are grouped as follows:
20 1.1 to 1.23 exemplify the basic process,
2.1 and 2.2 ha~e a preliminary coating applied to the solid
disperse phase,
3.1 is a double coating process in which the solid disperse
phase melts during processing,
4.1 to 4.4 exemplify double coating processes ln which the
solid disperse phase does not melt. In Examples 3.1 and
4.1 to 4.4 the outer coating is water-insoluble and has a
19
low~er melting point than the first coating,
5.1 to 5.5 exemplify use of both liquid and solid disperse
phases,
6.1 to 6.6 exemplify further coating materials.
Some discussion of particle sizes and properties
is also given.
A number of materials are referred to by trade
names or abbreviations. A key to these is as follows:
Coating Materials
10 PEG: Polyethylene glycol - number following PEG
indicates molecular weight (Mw), ex Fluka AG
PEO: Polyethylene oxide - number following PEO
indicates Mw, ex Aldrich
PVP: Polyvinylpyrrolidone - number following PVP
indicates Mw, ex Aldrich
PCL: Poly(caprolactone); Melting point = 60; ex
Aldrich
AC680: Oxidised polyethylene, (Mw = 2000): ex Allied-
Signal
AC400: Ethylene - vinyl acetate copolymer Mw = 3500,
Vinyl acetate content = 30~; ex Allied-Signal
AC5120: Ethylene - acrylic acid copolymer, Mw = 3500, Acid
number = 120mg KOH/g; ex Allied-Signal
Rigidex
XGR 791: High density polyethylene homopolymer Mw= 1.1 x
105; ex PP Chemicals
PCL-diol: Poly(caprolactone)diol: Melting point = 45C, ex
Aldrich
PAA 2000: Poly~acrylic acid). Number proceeding PAA
indicates Mw; ex Aldrich
Paraffin
W~x
(49C): Wax with melting point of 49~C, ex Fisons
2~
PEG 6000
ML: Polyethylene glycol (molecular weight = 6000)
monolaurate. Melting point = 61C; hydrophile -
lipophile balance 19.2 (water-soluble); ex Stephan
Europe
PEG 6000
DS: Polyethylene glycol (molecular weight = 6000)
distearate. Melting point = 55C; hydrophile -
lipophile balance = 18.4 ~water-soluble); ex
Courtaulds Chemicals
PEG 200
DS: Polyethylene glycol (molecular weight = 200)
distearate. Melting point = 34C; hydrophile -
lipophile balance = 5.0 (dispersible hot in
water); ex Courtaulds Chemicals
Synperonic
A7: Ethoxylated alcohol. Pour point = 21C;
hydrophile - lipophile balance = 12.2 (water
dispersible) ex Shell Chemicals
Solid Dispersed Phase
TAED: Tetra-acetyl ethylene diamine, ex BDH
SDCCA: Sodium dichloro isocyanurate dihydrate, ex BDH
Arosurf
TA-100: Distearyl dimethyl ammonium chloride (cationic
surfactant with melting point approx 75C) ex
Sherex
Light Soda
Ash: Anhydrous and porous sodium carbonate (ex ICI)
Particle size: 120um; total intrusion volume:
1.14cm3/gram
Microsil
GP: Porous silica (ex Crosfield Chemical) Particle
size: lO~m; BET surface area: 210m2/gram
Crumbling Agents
Aerosil
380: Pyrogenic silica (ex Degussa), particle size 7nm
Aerosil
R972: Pyrogenic hydrophobed silica (ex Degussa),
particle size 16r~
2 1
Avicel
PH-101: Microcrystalline cellulose (ex FMC Corp) particle
size = 50~m
Starch: Particle size = 5~m, (ex BDH)
~entone
SD-~L: Clay, particle size <l~m (ex NL Chemicals)
TSPP: Tetrasodium pyrophosphate, ex BDH
Surfactants
Arquad0 2HT: Di(hydrogenated tallowalkyl) dimethyl ammonium
chloride, ex Akzo
DC 193: Silicone glycol copolymer, ex Dow Corning
Span 85: Sorbitone trioleate (a nonionic surfactant) ex ICI
Examples 1.1 to 1.23
A process was carried out using a variety of
materials for the solid disperse phase and a variety of
organic coating materials. In most of these examples
surfactant was unnecessary and was not used. The procedure
was the same in each case, except in Examples 1.22 and 1.23.
The coating material was melted in a Z-blade mixer of lKg
capacity equipped with heating and cooling facilities. The
solid disperse phase was added at a temperature about 10 to
15C above the melting point o the coating material and
after a homogeneous mix had been obtained, cooling of the
mixture was started. When the temperature was within 5C of
the melting point of the coating material 65% of the
crumbling agent was added and then the temperature was held
constant while mixing was continued to allow full
incorporation of the crumbling agent. At this stage the
22
mixture formed lar~e agylomerates, and the remainder of the
crumbling agent was added.
Motor torque, which was representative of
viscosity~ was monitored. It was observed that the torque
rose steadily as the melt cooled towards the melting point
of the coating material. When the crumbling agent was
added the mixer torque dropped dramatically.
Mixing was continued while the temperature of the
mixer was allowed to decrease to 30C below the melting
point of the coating material over a period of 30 minutes.
Examples 1.22 and 1.23 used porous solid disperse
phases with liquids absorbed by them. For Example 1.22 the
disperse phase was light soda ash carrying absorbed silicone
antifoam. For Example 1.23 the disperse phase was silica
carrying absorbed perfume.
In these two examples the processing procedure
commenced with solid disperse phase placed in the Z-blade
mixer at a temperature about 10.C above the melting point
of the coating material. The coating material was added
progressively at a temperature 5.C above its melting
point. As soon as a melt began to form, as indicated by
formation of large agglomerates of the disperse phase, the
crumbling agent was added and cooling of the mixer
commenced. Again mixing was continued until the temperature
had fallen to 30C below the melting point of the coating
material.
In each of these examples the final product
obtained had the appearance of a dry particulate solid.
23
The materials used in Examples 1.1 to 1.23 are set
out in Table 1 below, which gives the amounts of the
materials as percentages by weight of the final particulate
composition.
24 ~ L~
TABLE 1
Example NoCoating Solid Crumbling
Material(s) Dispersed Agent
Phase
1.1 2% PEG 600 60% TAED 20% TAED
18% PEG 35000
1.2 2% PEG 600 60% TAED 20~ TAED
18% PEG 4000
1.3 20% PEG 35000 60% TAED 15~ AEROSIL 380
5% PEO 200 000
. _ _
1.4 15% PEG 35000 75% TAED 5% AEROSIL 380
5% PEO 200 000
_
1.5 12% PEG 40060% TAED 10% AEROSIL 380
18% PVP ~4000
.
1.6 20% PCL 65~ TAED 5~ AEROSIL 380
10% AC 680
.
1.7 16~ PEG 20000 60% NaCl 16% Starch
8% PCL
_
1.8 16% PEG 20000 60% NaCl lÇ% AVICEL PH-101
8% PCL
1.9 25% PEG 20000 65% TAED 10% AEROSIL 380
1.10 25% PEG 20000 65% TAED 10% BENTONE SD-2
1.11 20% PEG 20000 65% TAED 10% AEROSIL 380
5% AC 400
. _
1.12 15% PEG 20000 65% TAED 10~ AEROSIL 380
10% AC 400
1.13 15~ PEG 20000 65~ TAED 10% AERQSIL 380
10% AC 5120
. . _ _
TABLE 1 CONTINUED
Example No Coating Solid Crumbling
Material(s) Dispersed Agent
Phase
_
1.14 20~ PEG 6000 65% NaCl 10% AEROSIL 380
5% PAA 2000
1.15 10% PEG 6000 65% NaCl 10~ AEROSIL 380
15~ PAA 2000
1.16 25% PEG 20000 65% NaCl 10% AEROSIL 380
151.17 25% PCL 65% NaCl 10% AEROSIL 380
1.18 15~ PEG 20000 65% NaCl 10% AEROSIL 380
10~ PCL
.
1.19 25% PCL 60% SDCCA 10~ AEROSIL R 972
5% AEROSIL 380
1.20 25~ RIGIDEX 65% SDCCA 10% AEROSIL 380
XGR 791
. _ _ _
251.21 25% PCL-diol 65% Sodium 10% AEROSIL 380
Perborate
. _ _ _ . . _
1.22 7.5~ Synper- 55% light 5% AEROSIL R972
-onic A7 soda ash
4.5% PVP 40000 25% silicone
3.0% PCL diol antifoam
. _ _ . . _
1.2320% PCL-diol 35% Microsil 5% AEROSIL 380
GP
40% perfume
The porous disperse phase used in Example 1.23 was
prepared by a route in which the porous silica (Microsil GP)
was initially coated with a methoxyl functional silane
coupling agent which forms a monolayer with a hydrophobic
26 X~ 4~
surface. The coupling agent was gamma-methacryloxypropyl
trimethoxy-silane (A174, ex union Carbide) with a monolayer
surface coverage capacity of 314m2/gram. Since Microsil GP
has a large surface area, full surface coverage requires
large amounts of silane and it reduces the pore ~olume of
silica. Therefore, only the surface and the outermost pores
of Microsil GP were coated, following the procedure below:
The full water holding capacity of Microsil GP was
determined to be 2.2 grams of water per gram of silica.
(Further addition of water resulted in the loss of free-flow
of the powder). Silica particles were filled with water to
80~ of their capacity. A sufficient amount of A174 silane
coupling agent was dissolved in n-pentane to make up a
solution able to occupy the rest of the pores left by water
(i.e. 20~ of the full absorbing capacity of the silica).
When the n-pentane solution was added to the silica already
wetted with water, the powder stopped being free-flowing.
Subsequently the n-pentane was e~aporated at room
temperature and silane A174 polymerised at 38C and 70~
relative humidity. The resulting surface-hydrophobed powder
was then dried under vacuum at 60C for 24 hours before
being allowed to absorb the perfume.
Examples 2.1 and 2.2
In these Examples, the surface of the solid
dispersed phase was given a preliminary coating. The
general procedure was that the solid dispersed phase was
~irst mixed with a suitable prelim~nary coating material
27 X ~
(i.e. surfactant or a liquid which may contain a surfactant)
in a Z-blade mixer at an elevated temperature T8. After a
sufficient period of mixing at temperature T., the
temperature of the mixer was reduced to some lO~C above the
melting point of the main (polymeric) coating material and
this molten polymer was added to obtain a homogeneous mix.
The temperature of the mixture was then reduced to a
temperature Tc which is approximately 5C above the melting
point of the polymer and 65~ of the crumbling agent was
added. Mixing was continued to allow full incorporation of
the crumbling agent. At this stage, the mixture started
forming large agglomerates. The remainder of the crumbling
agent was added and the temperature of the mixer was allowed
to drop 30C below the melting point of the polymer. The
compositions of the coated particles prepared according to
the above procedure are given in Table 2.
In the Example 2.1, only a surfactant was used to
provide compatibility between NaCl and polymeric coating.
In the Example 2.2, the solid dispersed phase was coated
with a liquid mixture comprising a silicone fluid and a
surfactant compatible with the solid dispersed phase and
polymeric coating material. The function of the silicone
fluid is to provide full surface coverage of the disperse
phase and also to isolate the potentially reactive solid
disperse phase during mlxing with polymer at elevated
temperatures.
2~g3~ 4
d~O dl0
~ ~ 0 ~ u~ ~
o
0 c~ ~
u~ O
O ~ O ~ 0 a:
~0 0 d~ O d~
~z ~8
~1
¦ C x
UEC~o ~ ~ N
~0 d~
O O
h C
9 0 dl)d~ d~
t`~
:Z
E t`i t`l
~C ~
29 2
Example 3.1
Particles were prepared having compositions in
accordance with Table 3 which also includes the relevant
temperatures attained in the Z-blade mixer during various
stages of the process. The process consisted of two stages.
In the first coating stage solid dispersed phase and a
polymeric coating material were melted together and mixed at
a temperature TMAX- 1 which was approximately 10C above the
me~ting point of the solid dispersed phase. When a
homogeneous melt was obtained, the melt was cooled down to
the temperature TCl which was just above the melting point
of the first coating material. Some crumbling agent was
added to induce crumbling. Cooling and mixing was continued
until temperature was reduced to TM I N which was below the
melting point of the second coating material. The
particulate product is now ready for the second stage of the
coating process.
In the second stage of the coating process, the
temperature was raised to TM~X 2 which was about 5-10C
above the melting point of the second coating mzterial which
was added molten at the same temperature TM A X _ Z while
continuing to mix. In general when the agglomeration of
particles is observed, it would be appropriate to reduce the
temperature, and/or add some more crumbling agent. In this
Example more crumbling agent was added at the same
temperature, after which the temperature was allowed to fall
to some 30C below the melting point of the second coating
material at a rate of approximately 1C per minute. The
2~
resulting particles consisted of solid dispersed phase
particles encapsulated with a polymer coat over which
another material formed an outer coat.
I _ Z~ 4
~ In
__
o
C
o- ~U 'U~
E c o
dP a,l
U U~: C
O U~
U ~ 0o
~ t:n ~ s~
U~ ~ C-,i ;~
c ,i ~ D.--3
ou ~ ~n
U ~ ~ X
a) o 0 o ~ d~
u~ ~ 3
l _ Z- .. __ ,
H ~.) O
U ~ ~
E~o
~ E _
U ~_ .
U ~_
,~
~ 00
O ~ S CO ~ ~
_ .. _ ..
a). ~ ~
U h ~ o ~
u~.~ Q~ a) ~ o t~
.C.a ~ d~ o ' u
~ .,,
_ O
~ ~ 0o
.~ J-- ~r
~ o ~ C~ ~
~ _, ~
___ ~
N aldu~Fx~
32 2~9'~
Examples 4.1 to 4.4
Particles were prepared having compositions in
accordance with Table 4. These particles have two coatings
in which the outer coat is water-insoluble and has lower
melting point than the material in the first coat. In this
respect these examples are similar to the Example 3.1 except
that in the Example 3.1, the solid dispersed phase is melted
with the first coat.
In the first coating stage, the first coating
material was mixed with the solid dispersed phase at an
elevated temperature TM A X 1 . After obtaining a homogeneous
mix, the melt was cooled down to the temperature TC1 just
above the melting point of the first coating material and a
crumbling agent was added. Cooling was continued until the
temperature of TM I N was reached. In the second coating
stage, the temperature of the particles from the first stage
was raised to T~ 2 and ~he second coating material was
added at this temperature. Mixing was continued until the
agglomeration of the particles was observed. At this stage
the temperature was lowered to a temperature Tc 2 just above
the melting point of the second coating material and a small
amount of crumbling agent was found to be sufficient to
obtain crumbling. These double coated particles were then
cooled to ambient temperature while continuing to mix.
In the Examples 4.2 and 4.4, the crumbling agents
used in the first coating stage can create large amounts of
heat and also act as water sink upon exposure to water.
2~
N ~ O ~ O
N
q~ ~
~:-- ~ O O ~ 0
~ . . U~ U'~ __ In, 11
V~ ~ ~ ~I _l
~:: C O @ h 0 CJ) 0
O E C O O O O 0 C
~_) ~ dP ~ olP ~A 0 ~ lr~ ~ ~o
C~ ~: ~ ~t) tl~ ~ ~ tT~ t~ ~ ~rl O
. . _ __ ... __
~O~ 0 ~ ~0 ~0 _i ~ ~ C
~ _ ~ ~ ~ ~0 ~ ~
U~ t~ ~o ~* ~lt o ~ 0
rl I~J ~ ~-) ~ ~ ~ (~ ~ ~ C
_ Il, ~ ~ t_)
dP X A l~ ~ ~ ~ X C
~a ~ tO ~o ~ o ~ CD ta ~ 0 ~
:~: ~ 3 _~_ ~ ~ -I 3 ~0 a) O
~ .. _ ~ C ~I
~2 ~ ~ O O ~ ~
_ ~ tr) ~ ~ r
~,Ot) u~ Ln u~
~E~`~ ~D ~O ~D t`
m .
~: _ a~
E~' t~ r~ a~ ~ x C ~
_ __ C E a~ X
C 0 ~ O _I C E
a) ~ o Il, ~ C,) C
~ ~ ~ U~ ~ ~ ~rl T~
Q ~ q~ E~ ~: ~ J~
~a ~ c o d~ oP O ~P C) a~
t5~ d~ co m O a: O E
c ~ a) ~ r
v 0 " Oo *O a u~ ~ ~ v u
~01_1 0 111 o~P m d~ d ~ o '~I ~E 1
U~ C~ N ~ O O ~)~ E ~ a~
--o-'-- ~ ~ x ~ a)
O U C ~O E
_ N O ~1-- 0 O
_ ~1 ~D ~ C~ ~1N E E
_I _ ~ ~t .1 (O E~ ~ E
_ c~ _~ ~` ~D~ ,c _~
~ ~ O ~ ~ ~ C~ 0~-X C E~ ll C
o~ t~ O d~ O d~ X~ ~ E
O t~ ~D ~ O ~D 0 ~O~ ` u
~: -'~ _, _ 3 ~o ~~E~Il
N aIdulex~ ~1 N
~.. __ ~ ~ _ ~ ~:~: Z E~
34
Examples 5.1 to 5.4
Particles were prepared having compositions in
accordance with Table 5 below. These include both solid and
liquid disperse phases. For these particles the polymeric
material could contain a suitable surfactant while the
silicone fluid or paraffin wax which constituted the liquid
disperse phase could also contain surfactant. The general
procedure was that the polymeric material was first heated
with its surfactant (if any) to obtain a mixture of the two.
The liquid phase was separately heated with its surfactant
(if any) to obtain a mixture of the two. After incorporating
the surfactants, if any were used, the polymeric material
and liquid disperse phase were heated together and mixed to
form an emulsion.
The emulsification was carried out in a static
mixer which consists of a series of short capillaries
separated by flow dividers to prevent channelling of the
fluid. ~he capillary diameter (D), capillary length (L),
capillary entry angle (01)' capillary exit angle (02 ~ total
flow rate of the continuous and dispersed phases (Q) and the
number of capillary units (N) are important factors in
achieving small dispersed phase droplet particles (<lO~m)
with a narrow size distribution. Since the viscosity of
the silicone antifoams and silicone fluid used in the
Examples 5.1 to 5.5 is extremely large compared with the
continuous phase viscosity, it is necessary to use
elongational flow fields to achleve emulsification. ~he
above static mixer provides such a flow field in which the
maximum rate of shear S~ and elongation E~ at each stage is
calculated from:
Sm= (32Q/~ D3)
E~=(lSQ/nD3) sin(01/2) i=1 (entry) i=2 (exit)
The above equation indicates that the entry/exit
angles should be large (i.e. ~1 = 02 = 180) and in order to
reduce the pressure drop across the mixer, L/D should be
small. The emu~sifications were carried out under the
following conditions:- Number of capillary units, N=8,
D=lmm, L/D = 2 and E~ = 3 x 105 s-1.
Emulsion emerging from the last capillary unit is
sprayed on to the solid dispersed phase which was heated in
the ~-blade mixer to the temperature of the emulsion.
Mixing was continued until a homogeneous mix had been
achieved.
Thereafter, as for Examples 1.1 to 1.21, the melt
was cooled to a temperature Tc just above the melting point
of the coating material, 65~ of the crumbling agent was
added and then when agglomeration was observed the remainder
of the crl~mbling agent was added while cooling the melt to
some 30C below the melting point of the coating material.
It was observed that the inclusion of ethylene
acrylic acid copolymer (AC 5120) in the coating material of
Example 5.5 was very useful. Firstly, this copolymer acted
as a very efficient emulsifier in emulsifying the silicone
antifoam. Secondly~ it increases the viscosity of the
continuous phase in the emulsion thus helping to reduce its
tendency to form a double emulsion and also to reduce the
2~
36
size of the dispersed silicone antifoam. Finally, it
increases the hardness of the continuous phase once it has
solidified.
Z~
~ _ _ _ .___ ~D ~ __ O
L U N j d~
rl ~ ~ ~ o't ~o
__, .
E~O t` u~ In O U~
~._
~ C ~ C _/
~ a ~ ¦ ~ ~ u
:~ ~ ~ ~ ~: 3 0~ 0~
c ~ ~ a c l ~ l c
o o ~ 9 o C o ~ E
~ ~ oOO o ~ o ~ ~ ~ G~
C ~_~ ~o o ,o o o ~o U~
0 Ga~ C~ oO0 S!~OoO ~0 ~10 ~ m
U ~ ~ oP O ~ d~ ~ la oP d~ .~
_ _ N~ D ~ P ~1 ~`I 3 ~ 1. *
' N ~ I dill~x ~ ~ -I ~ 117 u~
,; .
;38 ~ 4
Particle Sizes
The average size and size distribution of the
coated particles were found to depend on a large number of
factors. These are: (1) raw material characteristics such
as size, concentration and surace chemistry of the solid
dispersed phase particles and crumbling agent, and molecular
weight and chemistry of the coating material(s), (2) process
conditions such as rotational speed of the mixer blades,
temperature of the mixer when the crumbling agent is added
and the type of mixer. In Table 6, the average size and
size distribution of the particles illustrated by various
Examples are tabulated.
Z~ 4
. .
~ z ~ o m ~ ~ c~
O_~ ~ C~ O CO ~D
E ~p ~ o 0 o
~1 t` ~ In ~7
~ C~ ~ ~ ePoo I O
C~ 1~ ~ ~1 _1 0 ~ ,
~ ~ ~1 O~ ~
~ N a~ ~1 ~ In ul O O t~ 11~ CO
a : ~ O~ o o 'a~
~ o ~, ~o~ ~ 0 o
H Ll 0 _
l C~l) 0~ ~ O O ~
~ h q) ~
O, :o C~ 1~'~o~ `
~ ~ ~c, Z' ' o ~ oCO
4~ ~ ~ ~ O ~
_ - o . ~
g ~ O 1-1 0 o u~ ~ E
N C E A N ~ V/ N ,~ .~ v N
Release Characteristics
The release characteristics of various
encapsulated particles placed in water were determined by
monitoring the concentration of the dispersed phase material
in water as a function of time. Final concentration of the
dispersed phase material after a prolonged time was also
determined. The release profiles of the particles are
expressed here as:- (1) delay time (tD) (if any) before
release commences: (2) initial rate of release (Ro; percent
release per unit time) and (3) half life of the encapsulated
dispersed phase (tH)~ These values are tabulated in Table
7. As seen in this Table, considerable variations in delay
time, initial release rate and half life of the dispersed
phase can be obtained.
~q q~ ~ c ~ o o ~ o o
C) ~ E --i ~I N 'D ~ .-1 ~ ~
C
C~ ~ ~ T~ ~ C~
_~
~7 ~ O O
~ ~ ~ ~ ~D
0~
W ~ ~ ~ C
~i ~ ~ Ti a E O
a ~; ~ _ o o Ln o o o o o
~: _ ._
:~ ~ ~--
U~ U~ E C~
a) a~ In U~ O O ~ ~ In
Z ~ E~-- N
tn
O ~
J' C
~:
E-rl Ll ~q ~a O 0 117 d~ O 11~ 0
o Q~ a) ~ ~ t~ o ~ u~ ~o o
o Z 3 ~ o a ~ _,
E~ ~
u~ ~ ~ o
~ ~ ~ ~ ~ ~o
~ ~ L~ ~ a
8 a ~o
D. E~
-o'
~ ~ .,~ _
U~ ~q O J~
,~ L~ ~ ~ X a~
o ~ ~ ~
~J ~1 01 0 ~ 3 ~
a~ a~
.. ~
t~ ~ O
~ ~ gO OC~ O
m ~ u~ 8o ~~ ~ o ~o o
O ~ ~
o ~ ~ x
o
O I ~ 3 1 !~ O
._.._ ._
Cn
m Q~ O E C~
.. ~ ~ ~o ~ ~ ~ _~
~ ~ O O X O ~ . . ~S . . .
t.~ 1 4 ~ Z E~
. _ . _ _ ~
42 2~
Notes on Table 7
1. Release of TAED in water is carried out at pH = 11.
2. Release of SDDCA in water is determined from the
measurement of available chlorine.
3. Release of Arosurf TA 100 in water is determined from
optical density measurements.
43 2~3~9~4
Example 6
Coated particles were prepared generally in
accordance with Example 1.22 but using different coating
materials. In some instances the coated particles were
coated again with a second coating material. In contrast to
Example 4, both coating materials were water-soluble. The
release of antifoam from the resulting particles was
determined by monitoring change in surface tension at 25C
and/or by monitoring the foam controlling action of the
particles.
Results are set out in Table 8 below.
Particles in accordance with Examples 6.2 and 6.3
were also subjected to agitation in a powder mixer for 15
minutes to test the durability of the coating. The release
of antifoam was not altered for Example 6.3 particles, and
increased only slightly for particles of Example 6.2, thus
illustrating the durability of their coatings.
39'~
44
~ ~
,~ C~ ,0,
0 0
~) 0 ~ 0
C~
~1 o
_l o
0 ~
4 ~ 0 ~ o 8 , ~ ~
o ~ e ~ 0 ~E
o ~: a~ (a a) 0 ~ a~
O ~1 0 ~1 a) 0 h _I O -
E ,~ Q~ t~ O Q. Q,4~ 0
O V o ~ o O ~ o ~ ~ E ~ o
~: c~ o ~ o ~ 0 ~ o
~q
v ~ 0 0~
,~ ,~ _I o ~ ~
0 0 h 0 ~ 0
.
co h ~ ~1 0~0 ~ h
a) ~ a~.c ~ u a~ cq o a~
~1 0 V ~~ o ~q tO 0
~: a~ ~ ~ ~10 ~ ~ E a~ ~ C.
E~ _I ~a 0 EE3 ~ ~I V~ o
a) .c to Ir) ~ o a~ ~ o
~ Z ~ ~ ~
o
~a~ V
,~ ~ ~ ~ ~
~0 O O
U dPO oPO ~PO
0 U~ O O O ~1 0
U U
E U E U O ,~ ,1 o
~ (~ ~ h t`~
,1 o rl (D h ~ 0 h
~ ~: O ~ ~ O ~ ~ ~ a E ~ E a
o ~ ~ 0 ~
0 0 O ~ OdP ~ ~ dP ~ dP T~
h d~ d ~1oP Ou~ ~a a) u) ~ ~ ~ a~
~1 Ir~ O ~ ~ ~ UO 4 O U df~ ~ O 0 ~ 0 0 ~ U dF'~4 I ~ ~ ~ 0 0 ~ 0 0 1~
o
z
_l
~J O
E ~
x 8 ~
W
