Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~049334
This invention relates to a process for coating water
soluble or water dispersible particles by means of the fluid bed
technique.
It is known to coat various particulate products having
a particle size of less than about 10 mm, preferably less than 1
mm, in order to minimize dust formation, e.g. enzyme containing
additives for detergent compositions in powder form. I-Iowever,
considerable difficulties have been experienced in performing
this coating. In practice it has hitherto been usual to utilize
coating agents dissolved in organic solvents rather than in water
when coating water soluble particles. The organic solvents have
to be evaporated and recovered at a later stage of the process
and may, furthermore, create a fire hazard and environmental
problems. If, on the other hand, the organic solvent is not
recovered, the coating process works in an uneconomical way~ ~ ~
Also, it is known to utilize the fluid bed technique to ~ -
coat various water soluble or water dispersible particles by
atomization of aqueous solutions of film forming, water soluble
coating agents, this process being described in Wurster's USA
patent No. 3,196,827. However, in this known process it is
difficult to avoid agglomeration of the particles to be coated,
and it is mentioned that this known process is only suited for
particles bigger than 30 mesh (ab. 0.6 mm). Also, by using
Wurster's method it is difficult to obtain thin coatings.
~ We have now found that it is possible to utilize an
; aqueous or substantially aqueous liquid for coating particulate
products having a particle size of less than about 1 mm in a
fluid bed process whereby particles can be coated with an
extremely thin coating and without substantial danger of
agglomeration.
More specifically, the process of the invention for
coating water soluble or water dispersible particles by means
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of the fluid be~ technique comprises introdllcing the particles
to be coated in a fluid bed reactor, the mean diameter of the
particles to be coated being in the ran~e of from 0.1 to 0.6 mm,
and introducing a coating fluid essentially consisting of an
aqueous or substantially aqueous solution or dispersion of a
macromolecular film forming, water soluble or water dispersible
coating agent by means of atomization, wherein the relative humi-
dity of the outlet air from the fluid bed reactor is below 100% and
wherein the maxirnum size of the atomized droplets of the coating
fluid does not exceed the minimum size of the particles ~ be coated.
The invention also relates to a coated product which
has a core of active substance formed particles having a diameter
of 0.1 - 0.6 mm, which core has a thin coating of a macromolecular
film forming substance.
If the maximum size of the atomized droplets of the
coating fluid exceeds the minimum size of the particles to be
coated, agglomeration will occur.
m us, by means of the invention agglomeration can be
avoided, and it is possible to perform the coating with a layer
20 as thin as about 0.1 - 10 ~, in a preferred embodiment 0.5
corresponding to about 1% of the dry particle weight. For a
given thickness of the layer of coating agent a larger amount of
coating agent, calculated on the particle weight, will be used
with decreasing particle size. This will appear from the
following Table I.
TABLE I
Amount of coating agent, calculated as percent by
weight of the particles to be coated
ALCALASE P * ALCALAS E M *
Thickness of Mean diameter of Mean diameter of
coatinq particles 400 ~ partic _s 700
0.5 ~ 0.8 % 0.5 %
1.0 ~ 1.5 % 0.9 %
* trademark
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~ lthough the coating produced according to the
invention in a preferred embodiment is very thin it is,
according to the invention, also possible to produce coatings
as thick as about 100 ~, if desired
The minimum size of the particles to be coated can
be determined by sieve analysis, and the maximum size of the
atomized droplets of coating fluid can be read from charts
available from the manufacturer of the nozzle, when the
viscosity of the fluid and the pressure is known.
In a preferred embodiment of the process according
to the invention the water soluble or water dispersible
particles to be coated contain one or more enzymes as an
active ingredient, e.g. proteases, amylases, lipases or
celluloses.
In another preferred embodiment of the process
according to the invention the enzyme or enzymes are bacterial
proteinases.
In another preferred embodiment of the process
according to the invention the bacterial proteinases are
precoated in order to reduce dust formation.
In another preferred embodiment of the process
according to the invention the bacterial proteinases are
ALCALASE P or ALCALASE M.
ALCALASE, which is a trade mark belonging to NOVO
INDUSTRI A/S, is a microbial proteinase. ALCALASE P is a
prilled ALCALASE. ALCALASE M is ALCALASE which is treated
by means of a Marumerizer as described in our British Patent
No. 1,362,365, issued on December 4, 1974, and in our published
French Patent No. 2,099,349.
In another preferred embodiment of the process
according to the invention the enzyme or enzymes are bacterial
or fungal carbohydrases.
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In another preferred embodiment of the process
according to the invention the bacterial amylases are
thermally stable amylases manufactured according to sritish
Patent No. 1,296,839.
In another preferred embodiment of the process
according to the invention the macromolecular film forming,
water soluble or water dispersible coating agent is a
cellulose derivative.
In another preferred embodiment of the process
according to the invention the cellulose derivative is methyl
cellulose, hydroxybutylmethyl cellulose, sodium carboxymethyl
cellulose, hydroxyethylmethyl cellulose or hydroxypropylmethyl
cellulose.
In another preferred embodiment of the process
according to the invention the macromolecular film forming,
water soluble or water dispersible coating agent is a
polyvinylpyrrolidone.
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~ n another preferred embodiment of the process according to
the in~ention t~le macromolecular film forming, water soluble or
water dispersable coating agent is a polyethylene glycol~
preferably of a molecular weight of between about 400 and about
6000.
In another preferred embodiment of the process according to
the invention the macromolecular film formingJ water soluble or
water dispersable coating agent is a methacrylic resin.
In another preferred embodiment of the process according to
the invention the macromolecular film forming, water soluble or
water dispersable coating agent is gelatine.
In another preferred embodiment of the process according to
the invention the coating fluid contains a-plasticizer.
In another preferred embodiment of the`process according to
the invention the plasticizer is a glycerol.
In another preferred embodiment of the process according to
the invention the glycerol is used in an amount of up to 60 % of
the dry weight of the coating agent, preferably in an amount of
between 10 and ~0 % of the dry weight of the coating agent.
In another preferred embodiment of the process according to
the invention the concentration of the macromolecular film forming,
water soluble or water dispersable coating agent in the coating
fluid is between 2 and 50 weight-%.
In another preferre'd embodiment of the process according to
the invention the concentration of the macromolecular film forming,
water soluble or water dispersable coating agent in the coating
fluid is between 4 and 10 weight-%.
In another preferred embodiment of the process according to
the invention the mean diameter of the particles to be coated is
between 0.1 and o.6 mm.
In another preferred embodiment of the process according to
the invention the mean diameter of the particles to be coated is
between 0.2 and o.6 mm.
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1ll anot~le~ p~eferred em'~o~imerlt of tile p~ocess according to
the invention the thlckness o~ the coating layer is be~ween
0.1 and 10 ~.
In another preferred embodiment o~ the process-according to
the invention ~he thickness of the coating layer is between
0.5 and 1 ~. -
The process according to the invention can be carried outin a continuous manner as well as batchwise. However, in a pre-
ferred embodiment of the invention the process is carried out
batchwise. In all the following examples the process is~ carried
out batchwise.
The invention also encompasses a coated product comprising
coated water soluble or water dispersable particles, whenever
prepared by means of the process according to the invention.
The water soluble or water dispersable particles can be of
any material which, for any reason, is to be coated. Examples of
materials encompassed are enzyme additives, e.g. proteolytic
enzyme additives for detergents, medicaments in pellet form, e.g.
oral penicillin preparations or hygroscopic substances, e.g.
fertilizers.
Coating of the particles is carried out for various reasons,
e.g. in order to minimize dust formation, to protect against
ultra-violet radiation, humidity or acidity, to minimize
contamination, and the like.
The coating agent can be any macromolecular film forming,
water soluble or water dispersable coating agent, e.g.
METHOCEL ~ MC 15: methyl cellulose of a methoxyl DS (Degree
of Substitution) of 1.64 to 1.92 and o~ a DP (Degree of Poly-
merization) corresponding to viscosities from 8 cP to 10,000 cP
in a 2 % aqueous solution at 20C.
TYLOSE ~ C 10: sodium carboxymethyl cellulose of a DS from
0.4 to 1.5 and a DP from 50 to 1000.
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TYLoS~ 20: methylhydroxyeth~l cellulose (or
hydroxyethylmethyl cellulose) of a methoxyl DS from 1.0 to
2.0, a hydroxyethyl DS from 0.1 to 0.5 and a DP from 50 to
1000.
l~ETHOCEL ~ XD 1181: hydroxypropylmethyl cellulose
of a methoxyl DS from 1.0 to 2.0, a hydroxypropyl DS from
0.1 to 0.5, and a DP from 50 to 1000.
KOLLIDON ~ K 25 PVP: polyvinylpyrrolidone of an
average molecular weight of 10,000, 40,000, 160,000 and
360,000 and mixtures thereof resulting in any intermediate
average molecular weight.
CAR~30WAX ~ : polyethylene glycols of average mole-
cular weights of 400, 600, 1000, 1540, 4000, 6000 and mixtures
thereof of any intermediate average molecular weight.
EUDRAGIT ~ E 30 D: methacrylic resins, aqueous
dispersions thereof. rrhis tablet lacquer is completely in-
soluble in alkaline liquids.
SOLUGEL ~ : gelatine.
Polypropylene glycols.
Polyvinyl alcohols.
Alginates.
The concentration of the coating agent in the aqueous
or substantially aqueous solution or dispersion corresponds to a
viscosity which is suitable for atomization. Usually, as
mentioned before, the concentration is between 2 and 50 weight-
%, preferably between 4 and 10 weight-%. The limits, however,
are highly dependent on the individual coating agent used. The
average diameter of the particles to be coated is usually
between 100 ~ and 600 to 1000 ~, preferably between 200 ~ and
600 ~. The relative humidity of the outlet air should usually
not exceed 60%. The temperature of the air, which is used to
fluidize the particles to be coated, should be adjusted in con-
sideration of the nature of the particles to be coated.
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Th~ (lualit~ o'~ t~ oatir,cr, is not; in~luenced by the shape of
the particles. F3y use of tile process of the invention it is possible
to produce a perf~ct coating on splleres and on irregularly shaped
particles as ~ell. Several of the known coating procedures are not
well adapted to the coating of irregularly shaped particles which li
are imperfectly coated, only. Therefore, the present process offers
special advantages in connection with the coating of irregularly
shaped particles. An example of such irregularly shaped particles
is a prilled enzyme product includin~ prilled ALCALASE or
ALCALASE P. When prilled ALCALASE is coated in accordance with
the invention a product consisting of irregularly shaped particles
having a-perfect coating is formed. Due to the irregular shape
these particles have a very raduced tendency to segregate from
the other particles of detergent compositions in powder form.
An additive consisting of spheroidal particles having a
density different from the density of the particles of the other
components of a powdery detergent composition will have a tendency
to segregate from said other particles and thereby create an
inhomogeneous detergent composition. The above irregularly shaped
particles therefore offer special advantages.
According to the invention the coating fluid may contain a
plasticizer such as triacetin, which is illustrated in the
following example 2.
By using glycerol as a plasticizer in the coating fluid
coated particles having specially advantageous dust levels can
be obtained according to the invention.
By using glycerol as a plasticizer in the coating fluid in an
amount of up to 60 per cent of the dry weight of the coating agent
or up to the point when the coated particles are beginning to
adhere to each other, preferably in an amount between 10 and ~0
per cent of the dry weight of the coating agent, the dust level
of the coated particles is reduced significantly which will appear
from the following.
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rn o~de~ l;o ~i~e a bet~er ur)t1erstarl~ing of how to correla~e
the different parameters of the process in order to obtain a
relative humidity o~ the outlet air of less than 100~ the following
calculation with reference to example 21 is presented. The inlet
air, which was the air in the plant, had the following charac-
teristics:
Temperature: 20C
Relative humidity: 50 ~ corresponding to 7 g of H20/kg air.
The rate of the coating fluidlwas 1700 ml/min. or 102
litre/hour. The coating fluid had a specific gravity of 1.0 g/cm~
and contained 10 % by weight of coating agent, corresponding to
a water inlet amount from the coating fluid of 91.8 kg/hour.
The rate of fluidizing air was 8000 N m~/hour or 9600 kg
of air/hour. Thus, the fluidizing air introduced 0.007 x 9600 =
67.2 kg of water in the systém per hour.
Thus, per hour a total of 91.8 + 67.2 kg of water was
introduced into the system. This corresponds to~159.0 kg of water,
which was removed from the system together with'about 9~00 kg of
air. As the outlet air had a temperature of between 2~and 27C
this amount of humidity in the outlet air corresponds to a
relative humidity in the outlet air of between 95 and 75 %. It is
noted that this relative humidity is within the limit given for
the relative humidity in claim 1.
In order to illustrate the invention the following examples
are presented.
- Examples l to 10 illustrate the preparation of the coating
fluid.
Example 1
Methyl cellulose (METHOCEL ~ MC 15) 50 g
Deionized water 1000 g
The methyl cellulose is triturated with about 33~ g of boiling
water, after which the rest of the water (optionally cold) is added
with s-ir~ing. The solutio~ is allowed to stand in a cold place.
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Exanple 2
Metilyl cellulose (ME~[~-IOCEL ~ MC 15) 50 g
Deioni~ed water 1000 g
Triacetin 5 g
A solution of methyl cellulose and deionized water is pre-
pared as described in Example 1, whereupon the triacetin is added.
Example 3
Sodium carboxymethyl cellulose (TYLOSE ~ C 10) 50 g
Deionlzed water 1000 g
The sodium carboxymethyl cellulose is dissolved in the water
with stirringJ using a high speed mixer.
Example 4
Sodium carboxymethyl cellulose (TYLOSE ~ C 10) 100 g
Deionized water 1000 g
The sodium carboxymethyl cellulose is dissolved in the water
with stirring~ using a high speed mixer.
Example 5
Methylhydroxyethyl cellulose ~YLOSE ~ MH 20) 50 g
Deionized water lOpO g
The methylhydroxyethyl cellulose is dissolved in the water
with stirring, using a high speed mixér.
Example 6
Hydroxypropylmethyl cellulose (METHOCEL ~ XD 1181) 50 g
Deionized water 1000 g
The hydroxypropylmethyl cellulose is dissolved in the water
with stirring, uslng a high speed mlxer.
Example 7
Gelatine (SOLUGEL ~ ) 50 g
Deionized water 1000 g
The gelatine is dissolved in the water with stirring, using
a high speed mixer.
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Example 8
Polyvinylpyrrolidone (KOLLIDON ~ K 25) 50 g
Deionized water 1000 g
The polyvinylpyrrolidone is dissolved in the water
with stirring, using a high speed mixer.
Example 9
Polyethylene glycol (CARBOWAX ~ 4000) 50 g
Deionized water 1000 g
The polyethylene glycol is dissolved in the water
with stirring, using a high speed mixer.
Example 10
Polyethylene glycol (CARBOWAX ~ 6000) 50 g
Deionized water 1000 g
The polyethylene glycol is dissolved in the water
with stirring, using a high speed mixer.
The solutions prepared according to Examples 1 to 10
are used for the coating of prilled ALCALASE (ALCALASE P) in
conventional and common fluid bed systems as stated in Examples
11 to 14 and 21.
Example 11 -
Apparatus: "STREBA-l" (Aeromatic AG,Basel)
ALCALASE P: 1000 g
Nozzle ~.
- Pressure 2 1/2 ato .
Internal diameter 0.8 mm ~ .
Inlet temperature of -:
fluidizing air: 41-43C
: Temperature of parti-
culate material: 31~-33C
; 30 Feed rate of coating
fluid: 6 1/2 ml/min.
Fluidizing air: 8-10 scale units
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1049334
~ a !rl D ~
.__
Apparatus: "WS(i-5" (W. Glatt, Haltingen,
Germany)
ALCALASE P: 6000 g
Mozzle
Position of jacket: 0.5
Pressure 1 1/2 ato.
Internal diameter: 1.2 mm
Inlet temperature of
fluidizing air: -~2-45C
Temperature of O
particulate material: 31 -33 C
Feed rate of
coating fluid: 35 ml/min.
Air velocity: 2 1/2 m/sec.
Example 13
. Apparatus: "WSG-30" (W. Glatt, Haltingen~
Germany)
ALCALASE P:. ~5,000 g
Nozzle
- Position of jacket: 0.3
Pressure: 6 ato.
Internal diameter: 1.8 mm
Inlet temperature of
fluidizing air: ~2-45C .
Temperature of O 0
particulate material: 31 -33 C
Feed rate of
coating fluid: 187 ml/min.
Fluidizing air: 5 scale units
Example 14
Apparatus: "STREBA-60" (Aeromatic AG, Basel)
ALCALASE P: 135 kg
Nozzle
Position of jacket: 1.0
Pressure: 6 ato.
Internal diameter: 2~ mm
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:i nlet te~ t,ure oP
fluidizing air: 42-l~5C
Temperat,ure of
particulate material: 31-3~C
Feed rate of
coating flu'id: 325 ml/min.
Rate Or fluidiæing air: corresponding to position 3
of damper.
In all cases particulate products are produced having remark-
ably good properties.
The amount of coating layer on the ~articles and the amount of
dust present in some of the coated products prepared according to
Examples 12 to 14 appear from the following table II.
Table II
Coating fluid Amount of Amount of dust
Example p~epared according coating layer on in ~g/100 g of prod~cr
No. to Example No.coated product Total Enzyme
1 1 % 20 2.1
1 1 % 20 1.6
6 1 % , 5 o.8
12 1 1/2 ~ 20 2.6
% 1 5 1 . 8
1 1 1/2 % 20 0. 8
6 2 % 10 1.1
3 % lo o.8 . -
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1 % 5 ~ 1.8
1 1/2 % 20 1.0
3 1 1 % 5 l.o
1 % lo 1.6
14 1 1/2 % 5o ~.4
1 1 % 15 1.6
Examples 15 to 20 illustrate the preparation of a coating fluid
containing glycerol and corresponding coating fluids without
glycerol.
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1~49334
~`xa.~t~
Methyl cell~llose (M~ HOCEL ~ MC 15) 50 g
Deioni,zed water 950 g
The methyl cellulose is triturated with about 33~ g Or boiling
water, after which the rest Or the water (optionally cold) is added
with stirring. The solution is allowed to stand in a cold place.
Example 16
Methyl cellulose (METHOCEL ~ MC 15) 42.5 g
Glycerol 7,5 g
Deionized water 950.0 g
A solution of methyl cellulose and deionized water is prepared
as described in Example 15, whereupon the glycerol is added.
Example 17
Sodium carboxymethyl cellulose (CELLOFAS ~ B 5) 100 g
Deionized water 900 g
The sodium carboxymethyl cellulose is triturated with about
3~3 g of boiling water, after which the rest of the water (optionally
cold) is added with stirring. The solution is allowed to stand in a
cold place.
Example 18
Sodium carboxymethyl cellulose (CELLOFAS ~ B 5) 85 g
Glycerol ~ 15-g
Deionized water 900 g
A solution of sodium carboxymethyl cellulose and deionized
water is prepared as described in Example 17, whereupon the
glycerol is added.
Example 19
Sodium carboxymethyl cellulose (CEKOL ~ HS) 10,0 g
Deionized water 900 g
A solution af sodium carboxymethyl cellulose and deionized
water is prepared as described in Example 17.
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~049334
E~ample 20
Sodium carbox~methyl cellulose (CEKOL ~ HS) 85 g
Glycerol 15 g
Deionized water goo g
A solution of sodium carboxymethyl cellulose and deionized
water is prepared as described in Example 17, whereupon the glycerol
is added.
The solutions prepared according to Examples 15 to 20 are used
for the co~ting o~ ALCALASE M in a fluid bed system as stated in
Example 21
Example 21
Apparatus: "WSG-300" (W. Glatt, Haltingen,
Gerrr~any)
ALCALASE M: 600 kg
Nozzle six-headed nozzle
Internal diameter: 1.2 mm -~
Jacket diameter: 6.o mm
Pressure: 6.o ato.
Inlet temperature of
fluidizing air: 46-50C
Temperature of
particulate material: 23-27C
Feed rate of
coating fluid: 1700 ml/min.
Fluidizing air: 8000 N m3/hour
In all cases particulate products are produced having rernark-
ably good properties, especially in regard to the dust level.
The amount Or dust present in the coated products prepared
according to Example 21 appears from the following table III.
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'ilat~Le-:r~:r
Coating ~ id Amount of Amount of dust
Example prepared accordil~K coating layer on in ug/100 g of~Eroduct
No. to E~'xarnple No. coated product Total Enzvme
. _ _ _ _ _Y
. 1 % 20 1.2
16 1 % 10 0.5
21 17 1 ~ 15 1.6
1~ 1 % 10 0.7
19 1 ~ 30 1.~
1 ~ 10 0.8
. . _
It appears from the above table III ~hat by using glycerol as a
plasticizer in the coating fluid a remarka'~ly advantageous effect on
the dust level of the coated particles is obtained.
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