Note: Descriptions are shown in the official language in which they were submitted.
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Case 7603(2)
RELEASABLY ENCAPSULATED_ACTIVE SUBSTRATES
The present invention relates to active substrates such as
bleach activators releasably encapsulated in a coating thereon and
methods of applying the same.
It is well known to use bleaches and bleach activators in
detergent formulations. One of the important aspects of such
formulations is that they should be capable of being stored over a
significantly long period both by the producers of such
formulations, the retailers of the product and by the end user,
e.g. the housewife, who usually buys in bulk and likes to use it in
small aliquots for washing as and when necessary. However, it is
also well recognised that the components of such formulations,
especially the bleaches and bleach activators, have an unacceptably
short storage life due to their tendency to undergo undesirable
physical or chemical changes, thereby resulting in deterioration of
the formulation which may manifest itself as, e.g. loss of activity,
discolouration, loss of attrition resistance, hydroscopicity and
hence caking by absorption of moisture, staining the clothes washed
or as malodour. It has besn found that the bleaches and bleach
activators in particular are prone to such undesirable changes~.
It has been known to apply protective barrier coatines on
relatively unstable compounds to improve their storage stability.
Catalysts used in chemical reactions are a well known example where
barrier coatings have been applied. In the case of active
substrates such as bleach activators there is the added problem thak
any coating applied should be such that:
(a) the active species is readily released when in contact with the
aqueous wash system,
(b) it mitigates any problems of dye damage or staining by the use
of a bleach activator
(c) the barrier coating itself should not interfere with the other
components in the formulation,
(d) the barrier coating does not adversely affect the wash or the
clothes being washed in term3 of causing dye damage or
staining, and
(e) should be user friendly and friendly towards the environment
: when discarded with the wash water.
It has now been found that the relative instability of active
substrates such as bleach activators or the risk of dye damage or
stainin~ thereby can be mitigated by encapsulating the substrate in
its powder or granular form in a barrier coating capable of
releasing the active substrate in the aqueous wash system without
adversely affecting the clothes being washed, the user or the
environment.
Accordingly, the present invention relates to an encapsulated
active substrate comprising a bleach activator releasably
encapsulated in a coating of at least one metal salt of an inorganic
acid, said salt being soluble in an aqueous medium such that upon
contacting the encapsulated substrate with the aqusous medium the
the active substrate is released into said medium.
By the term "active substrate" as used herein and throughout
the specification is meant a bleach activator as such or a composite
which comprises such bleach activator and one or more other
components including conventional binders such as e.g. a bentonite
clay; surfactants such as polyoxyalkylene sorbitan oleate esters,
e.g. Tween (Registered Trade Mark) an alkali metal salt of a
; polycarboxylic acid, e.g. Dispex-G40 (Registered Trade Mark, exAllied Colloids, UK); disintegrating aids such as cross-linked
carboxy methyl cellulose derivatives e.g. Ac-di-sol (Registared
Trade Mark) or a polyacrylate; and fillers such as the cellulosic
type, e.g. Avicel (Registered Trade Mark).
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The bleach activator in the active substrate suitably comprises
at least one compound selected from a cyclic anhydride of the
structural formula (I) or a lactone of the structural formula (II)
below:
0 0
~0 ~
\ N N
R
~I) (II)
wherein Q is a divalent organic grouping such that Q and N together
with the carbonyl and oxygen functions form one or more cyclic
structures and in (I) R is H, an alkyl, aryl, halogen, a carboxylic
or a carbonyl containing function, and in (II) R is a C2 or higher
alkyl, alkaryl, aryl, aralkyl, alkoxyl, haloalkyl, amino, amino
alkyl, dialkyl amino, carboxylic or a carbonyl-containing function.
Bleach activators of formula (I) are claimed and described in
our published EP-A-331300 and those of formula (II) are claimed and
described in our published EP-A-332294 and are incorporated herein
by reference.
In particular, such compounds include bleach activators such as
2-hydrocarbyl (4H) 3,1-benzoxazin-4-ones (especially the 2-methyl
and 2-aryl derivatives), the 2-N,N-dialkylamino (4H)
3,1-benzoxazin-4-ones (especially the 2-N,N-dimethyl derivative) and
isatoic anhydride and its homologues and derivatives. Bleach
activators described in publish~d EP-A-170386
(N-alkoyl-6-aminoperoxycarboxylic acids and their salts) and in
GB-A-2832021 (tetraacetyl ethylene diamine) can also be encapsulated
in a coating to improve their stability and are incorporated herein
by reference.
The term "aqueous medium" as used herein and throughout the
specification is meant to include the aqueous alkaline medium
encountered in a wash cycle or during a washing procedure.
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The metal salts of inorganic acids which can be used to form
the encapsulating coating must be soluble in the aqueous medium
although it would be advantageous if they are soluble in water. The
solubility should preferably be at least 3g/lOOg of the aqueous
medium at ambient temperatures, eE 15C, although the 8reater the
solubility, the better. Examples of such compounds include the
water soluble carbonates, sulphates and phosphates of the metals in
Groups I-III of the Periodic Table!, especially the alkali metals,
some alkaline earth metals such as~ magnesium, zinc and Group III
metals such as aluminium. Particularly preferred are the sulphates
and phosphates of sodium, potassium, zinc and aluminium. Whichever
metal salt is chosen, the salt should be such that it is capable of
forming an encapsulating barrier coating on the active substrate.
In the case of some compounds of the structure type (II),
especially if the compound is a 2-aryl substituted benzoxazin-4-
one, such activators cause dye damage. The performance of such
activators can be improved by using an encapsulating coating of a
zinc salt such as zinc sulphate. On the other hand, with activators
of the type (I) ie those having an isatoic anhydride type structure,
the problems of staining and dye damage can be mitigated by using an
encapsulating coating of an aluminium salt such as aluminium
sulphate.
The encapsulating coating should suitably form a minor
proportion of the encapsulated product. That is, the active
substrate should be at least 50% w/w of the encapsulated product,
preferably greater than 65% w/w of the encapsulated product and most
preferably from 65-ôO% w/w.
Ideally, the thickness of the coating encapsulating the active
substrate is suitably such that it does not peel off or is not
readily removed by attrition and is preferably at least 0.03
micrometers.
The encapsulation should however be such that it completely
covers the active substrate coated. The active substrate is
suitably in the form of a powder or granules prior to
encapsulation. The initial particle size of the substrate should be
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., . ; . ~
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preferably from 50-200 micromaters for the powder and from 200-2000
micrometers for the granules. Substrates having particle sizes
within this range can be producecl from commercially available
material by milling and/or grinding, granulation or preferably by
the technique of extrusion and spheronisation. In producing the
powder or granules of the active substrate they may be in the form
of a composite comprising the bleach activator, binders, dispersing
aids, surfactants and fillers as described above. The encapsulating
coating can be applied on the substrate by conventional means. It
is preferable to create a fluidised bed of the substrate particles
and to spray them with a solution of the metal salt. In using this
technique the conditions should be controlled carefully in order to
achieve satisfactory encapsulation. ~or instance, the fluidisation
of the substrate particles should be such that they float in the
fluidising medium as separate and distinct particles for a
sufficiently long time in the coating environment so as to enable
the spray of the metal salt to substantially completely encapsulate
and hermetically seal substantially all of the particles
individually. At the same time the residence time within the
coating environment and the temperature within the coating
environment should be such that before the encapsulated particles
emerge from the environment they are substantially dry and resistant
to (a) loss of coating by attrition and (b) agglomeration. In this
context the choice of a fluidising medium is also important in that
it should be substantially inert to the encapsulating process and
should not adversely affect the nature of the substrate being
encapsulated or the encapsulating coating. An example of a suitable
fluidising medium is air.
The present invention is further illustrated with reference to
the following Example.
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Example_l
In the Example below the following components were used in a
formulation to produce the active substrate:
Isatoic anhydride (bleach activator) 80% w/w
Bentonite clay (binder)9% w/w
Ac-di-sol* (disintegrating aid) 2% w/w
Avicel* (a cellulosic filler) 9% w/w
* Registered Trade Mark
The above components ware formed into a dough in water and
subjected to extrusion followed by sphsronisation to obtain granules
having a particle siz& of 500 1000 micrometers.
The granules were then fluidised in a Strea-1 fluidiser at a
spray rate of about 6g/min through two-fluid nozzle with atomising
air pressure of about 0.8 bar.
Air was used as the fluidising medium at an air volume of 10
units on Strea 1. The inlet air temperature was 48C and the outlet
air temperature was 36C.
A solution of 150g of anhydrous sodium sulphate in 700g of
water was used as the encapsulating solution.
This sodium sulphate solution was sprayed in a direction
cocurrent with the fluidising air using a Wurster column. ThP
spraying of the solution took about 1.5 hours to encapsulate the
granules. The encapsulated granules were then dried for a urther
20 minutes during which time the temperature was increased to 52C
at the inlet and 46C at the outlet to bake the encapsulating
coating into a solid, dry barrier.
The encapsulated granules so produced were mixed at a
concentration of 5% w/w with a detergent powder containing 80% w/w
ECE Base (ex Westlairds Limited, North Green, Datchet, Slough
SL3 9JH, Berkshire, UK) and 15% w/w of a perborate bleach and stored
in open packs at 37C and 70% relative humidity. The resultant
detergent formulation did not suffer any discolouration or
substantial loss of activity after storage for 2 months.
That the solubility of the coating in the aqueous medium is
unaffected is illustrated by a comparison of coated and uncoated
'
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spheres made with the above formulation where it can be seen that
there is no significant difference between whole and crushed
spheres:
Test conditions : 40C, 2.5% active isatoic anhydride (hereafter
"IA") was used in detergent base containing sodium
perborate tetrallydrate. Washes were carried out
in a Terg-o-tometer over a period of 20 minutes.
5.85g of detergHnt base plus 0.15g of bleach
activator at 10()Z active were used i.e. 0.3g of
formulated isatoic anhydride spheres.
Substrate Cloths: EMPA 114 Red wine stain and WPK BC-l tea stain
Measurements : Reflectance measurements were taken with
ICS-Texicon Micromatch spectrometer. Results are
expressed as percentage stain removal (%SR)
calculated from the following expression:
L(final)-L(initial)
%SR 5 ------------------- X 1OO
L(standard)-L(final)
L(final)- final reflectance value
L(initial)= initial reflectance value
L(standard)= standard reflectance value
L value is reflectance value as defined in
Committee Internationale D'Eclarage LAB system
(CIELAB).
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FORM EMPA TEA
Isatoic Anhydride (ex BASF) 70.09 29.52
whole spheres as per formulation Coated with Na2SO4 69.37 28.78
50% active in IA
crushed spheres as per formulation " " " 69.58 28.91
Tetra Acetyl Ethylene Diamine (Pure, ex Warwick 66.84 22.07
Int.)
BlankDetergent base alone 60.99 13.04
Isatoic Anhydride53-106 micrometers 69.21 28.35
35 least significant difference) 1.22
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Example 2
Granules containing 80X isatolc anhydride bleach activator were
encapsulated with the inorganic salts detailed below. These coated
granules (20 parts) were mixed with a phosphate-free detergent base
which contained 25% sodium perbor,ate monohydrate (80 parts).
Samples from the detergent formul,ations thus prepared were then
spread in narrow strips of ca. 2cln width onto a test cloth of white
cotton (EMPA 221). This cloth had previously been placed in a tray
and dampened with sufficient wate:r,to absorb into and dampen the
strips of detergent formulation. After 30 minutes the cotton test
cloth was thoroughly rinsed in running tap water and air dried.
The above test was repeated a further three tlmes. A panel of
five observers was then used to compare the extent of brown staining
of the cotton cloths under artificial daylight (D65) illumination in
an ICS-Texicon light cabinet. Each observer was asked to score the
staining underneath the detergent strips on a scale of 1 to 5
where;- cloth(s) with least staining = 1, and cloth(s) with most
staining = 5.
'~ The marks obtained are given below.
,, 20
Formulation containing Mean
bleach activator score
encapsulated with;
Zinc sulphate heptahydrate (ca. 38% w/w) 1.10
25 Zinc sulphate heptahydrate (ca. 31% w/w) 1,40
Zinc sulphate heptahydrate (ca. 25% w/w) 1.65
` Aluminium sulphate hexadecahydrate (ca. 38% w/w) 2.05
Aluminium sulphate hexadecahydrate (ca. 31% w/w) 2.45
Aluminium sulphate hexadecahydrate (ca. 25% w/w) 3.40
Sodium acetate (ca. 38~ w/w) 5.00
The results show that the bleach activator granules
encapsulated with the zinc and aluminium salts exhibit significantly
reduced tendency for staining of the test fabric than those
encapsulated with a salt of an organic acid.
Example 3
Granules containing 82% 2-phenyl benzoxazine-4-one (2PB4)
bleach activator were encapsulated with the inorganic salts detailed
below. These coated granules (20 parts) were mixed with a
phosphate-free detergent base whi,h contained 25% sodium perborate
monohydrate (80 parts). Samples from the detergent formulations
thus prepared were then spread in narrow strips of ca. 2cm width
onto a test cloth of cotton dyed with immedial black (~MPA 115).
This cloth had previously been placed in a tray and dampened with
sufficient water to absorb into and dampen the strips of detergent
formulation. After 30 minutes th~ cotton test cloth was thoroughly
rinsed in running tap water and air dried. The above test was
repeated.
Reflectance measurements were taken with an ICS-Texicon
Mlcromatch Spectrometer. The average results from 10 readings from
underneath each test strip on each test cloth are expressed as
percentage stain removal (%SR).
Composition of 2PB4 granules;-
2PB4 82% w/w
Bentonite clay 13~ w/w
Dispex G402% w/w
25 Avicel 3% w/w
Formulation containing 2PB4 bleach %SR
activator encapsulated with;
Aluminium sulphate (ca. 38% w/w coating) 14.4
Zinc sulphate (ca. 38% w/w coating) 13.7
Uncoated granules 27.6
Visual observations confirmed the marked reduction of
'pinholing' dye damage for the zinc and aluminium suphate coated
granules when compared with uncoated granules.
The results show that the bleach activator granules
encapsulated with the zinc and aluminium salts exhibit significantly
reduced tendency for dye damage.
