Note: Descriptions are shown in the official language in which they were submitted.
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BLEACH ~CTIVATOR GRANULES
The invention relates to bleach activator granules for use in or with
a detergent and/or bleach composition and the preparation of said
bleach activator granules.
Detergent compositions which contain so-called organic bleach
activators in addition to the usual detergent substances having a
cleaning action, builders and bleaching materials, are known. A class
of bleaching materials which are commonly used is that which
provides hydrogen peroxide in solution. Examples of this class are
sodium perborate, sodium percarbonate, sodium perphosphate, sodium
persilicate and urea hydrogen peroxide. These compounds will herein- -
after be reFerred to as "percompounds". The most commonly used
percompound in detergent composltions is alkali metal perborate.
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The organic bleach activators referred to herein increase the
bleaching action of percompounds,e.g. sodium perborate, in that they
are believed to react with the hydrogen peroxide to form peracids, a
bleaching species which~ unlike sodium perborate, is active at
- lower temperatures,e~g. 40-60C.
Examples of~solid organic bleach activators for percompounds known
in the art are carboxylic anhydrides, for example succinic, benzoic
;~ and phthalic anhydrides, carboxylic acid esters, For example sodium
acetoxybenze~ sulphonate,sodium para sulphonated phenyl benzoate and
acetyl salicylic acid; N-acyl substituted amides, for example tetra-
acetyl ethylene (or methylene) diamine and tetra-acetylglycoluril.
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Since organic bleach activators are generally hydrolysable com-
pounds which on direct incorporation in detergent com~ositions
tend to hydrolyse or perhydrolyse owing to the action of ~oisture,
alkaline substance and the percompound in the detergent composi-
tion, and to attack oxidation-sensitive ingredients, they are
generally protected from said in~luences.
The most common way oE protecting bleach activators is by provid-
ing the bleach activators in the form of coarse granules as
agglomerates or coated particles.
Various methods of preparation o granulated and/or coated bleach
activator particles and use of said bleach activator particles
in detergent compositions have been described in the literature.
In the majority of cases an organic substance or a mixture of
organic substances is used as the binding or coating material,
such as nonionic surfactants, fatty acids, polymeric materials
and waxes (see e.g. US Patent Specification ~,003,8~1; US Patent
Specification 3,975,280; British Patent Specificatio~n 1,398,785,
and British Patent Specification 907,358. Use of organic sub-
stances as binding or coating material has the disadvantage that
it generally~gives handling problems, especially in hot seasons,
due to stickiness, and also that the rate of solution is often
low, due to increased granule disintegration time.
¦ British Patent Specification No. 1,360,427 descrihes coated
activator particles constituting 5-50% by weight of bleach acti-
vator and a ~airly hiyh proportion, i.e. 95-50~ by weight, o~
an inorganic coating material comprising sodium triphosphate.
i 30 The disadvantage of such granules is that they are insuf~iciently
soluble in the wash liquor and have unsatis~actory disintegration
properties.
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¦ Any proper method of protecting the bleach activator against the
environment must allow dissolution of the activator in the wash
liquor. Release of the activator must be achieved at a period
I well before the end of the wash cycle so as to give time or the
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bleaching step to occur. Preferably this should occur as early as
possible in the wash cycle for maximum bleaching to occur.
It is thus clear that in order to produce a satisfatory bleach
activator granule for use in a detergent bleach composition, the
choice of a suitable binding agent is of essential importance.
One important requirement for a good binding material is good
water-solubility so as to impart satisfactory disintegration
properties to the granule. Other important requirements are:
- a good binding capacity, so as to form fairly strong granules
with good resistance to break-down through mechanical action
during handling, transport and storage,i.e. mechanical strength
- formulation-compatible,e.g. suitable pHi
- capable of producing granules with a high activator content,
and preferably,
- inexpensive and readily availabe.
Bleach activator granules hittlerto known in the art are deficient
in some or other respects.
It is therefore an object of the present invention to provide
improved bleach activator granules having the necessary attributes
for a suitable use in or with washing and bleaching compositions.
According to the invention a bleach activator is provided in the
form of granules for use in or with washing and bleaching
compositions of a size of from 0.2 mm to 2.5 mm, which granules
constitute from 55% by weight up to about 90% by weight of at least
one bleach activator for percompounds, having a titre in the
defined peracid formation test of at least 1.5 ml 0.1N sodium
thiosulphate, and from 10% to 45% by weight of a binding material
comprising essentially a mixture of at least two hydratable
inorganic salts. The first hydratable salt is either sodium tri-
phosphate or borax (Na2B407) or a mixture thereof and the second
hydratable inorganic sal~ is a salt having solubility in water of
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more than 30 grams anhydrous salt per 100 ml at 60C, a pH of
around neutral up to about 11, for 10% solution, and no transition
point below 35C.
The peracid forlnation test is a well-known test method for selecting
suitable bleach activators. It has been described in US Patent
Specification No. 3,177,148 and is as follows:
Peracid formation test:
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A test solution is prepared by dissolving the following materials
in 1000 ml distilled ~ater:
sodium pyrophosphate (Na4P207.10~l20) - 2.5 g
sodium perborate (NaB02.H~02.3H20) havin~
15 10.4% available oxygen - 0.615 g
sodium dodecylbenzene sulphonate - 0.5 9
To this solution at 60C such an amount of activator is added that
for each atom of available oxygen present one molecular equivalent
of activator is introduced.
The mixture obtained by addition of the activator is vigorously
stirred and maintained at 60C. After 5 minutes from the addition
a 100 ml portion of the solution is withdrawn and immediately
pipetted onto a mixture of 250 g. cracked ice and 15 ml glacial
acetic acid. Potassium iodine (0.4 9) is then added and the liberated
iodine is immediately titrated with 0.1N sodium thiosulphate with
- starch as indicator until the first disappearance of the blue colour.
The amount of sodium thiosulphate solution used in ml. is the titre
of the bleach activator.
Examples o~ bleach activators utilisable according to the invention
may be compounds of the class of carboxylic anhydrides; carboxylic
acid esters; and ~-acyl or 0-acyl substituted amides or aminesi such
as sodium acetoxybenzene sulphonate (SABS)~ sodium para sulphonated
phenyl benzoate, acetyl salicylic acid, tetraacetyl methylene
diamine (TAMD), tetraacetylethylene diamine (TAED), and tetra-
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acetylglycoluril (TAGU).
Preferred bleach activators are TAMD and TAED.
An essential feature of the bleach activator granule of the
invention is that the binding material constitutes a mixture of
at least two components,i.e. a first hydratable salt which is sodium
triphosphate and/or borax and a second hydratable salt as defined
above. For reasons of costs ancl practicability sodium triphosphate
is preferably used as the first hydratable salt.
The presence of sodium triphosphate and/or borax is essential in
that it governs the final strength of the granule, whereas the
presence of the second hydratable salt is needed to govern the --
stickiness and intermediate strength of the agglomerate during the
preparation of the granules.
The second hydratable salt should have no transition point below
35C, preferably at least 37C. This limitation is deemed
necessary for maintaining particle stability under fluctuating
and/or severe storage conditions. A transition point lower than
35C would increase the risk of the granules to disintegrate and
decompose during storage through loss of water of hydration.
High sollibility of the second hydratable salt is not only of
importance for the release of the activator but also for providing
a relatively fast disintegrating rate of the granule. The latter
is of importance to reduce mechanical loss in the washing machine
and to reduce the risk of "spotting" on clothes soaked therein.
"Mechanical loss" is a term used here to indicate the proportion
of generally less soluble or heavy particles of the cleaning
composition, sinking into the bottom of the washing machine and
thereby excluded from contributing in the active washing pro oess.
The pH in solution is important since higher alkalinity would
present problems in spraying and handling and would affect enzyme
stability in the product as well as that of the activator itself.
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A suitable pH range is from about 6 to 11, preferably from 7 to 10,
so as to have the least effect on the overall in use pH of the
washing composition.
Preferably the proportion of sodium triphosphate and/or borax in
the granule o-f the invention will be within the range of about 5%
to 35% by weight based on the total granule composition. Though a
proportion smaller than 5% can be used,it is not advisable since it
will tend to give granules of unacceptable mechanical strength. A
par-ticularly suitable proportional range of sodium triphosphate
and/or borax is from about 7.5-30% by weight, based on the total
granule composition.
Advantageously the second hydratable salt in the granule of the
invention is present in a proportion ranging from about 5 to 30%
by weight, preferably from 5 to 15% by weight based on the total
granule composition.
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There are no specific requirements as to the ratio by weight of the
first hydratable salt to the second hydratablesalt.Various ratiosare
possible and the selection thereof for each particular case will
be no problem to the man skilled in the art working ~ithin the
invention.
A particularly suitable second hydratable salt for use in the present
invention is disodium orthophosphate. Other examples of suitable
compounds are potassium triphosphate and magnesium sulphate.
Inorganic salts, such as sodium carbonate, sodium silicate, sodium
sulphate, sodium chloride, trisodium orthophosphate, sodium tri-
phosphate and sodium pyrophosphate are deficient in one or more
respects and are therefore unsuitable for use in the present
invention. Sodium carbonate is unsuitable on account of its high
pH in solution and its low transition point; sodium silicate and
trisodium orthophosphate are unsuitable in view of their high pH
in solution; sodium chloride is unsuitable as it does not form a
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hydrate under normal conditions; sodium sulphate is unsuitable owing
to its low transition point; sodium triphosphate and pyrophosphate
are deficient in their low solubility.
Disodium orthophosphate (DSOP) has a solubility in water of over
40% as anhydrous salt at 60C; a pH for 10% solution of about
8.9 and a transition point of >35C. Furthermore this salt has a
number of hydrates which give it high water-binding capacity.
It was also found that 50% solutions of the dihydrate, which are in
: 10 completely solid form at ambient temperature, are fluid and
sprayable at temperatures above 50C.
Magnesium sulphate has a solubility in water of about 35% as
anhydrous salt at 60G; a pH for 10% solution of about 7 and
no transition point below 35C.
Examples I-II
Some batchwise granulation experiments were carried out using an
N,N,N',N'-tetraace-tylethylene diamine (TAED), sodium triphosphate
(STP) mixture, containing about 85% by weigh-t of TAED.
First experiment
4.5 kg of said TAED/STP mixture were placed iln a 0.5 metre pan.
A solution containing 49% of disodium orthophosphate dihydrate
was prepared. 1.25 kg of this solution at a temperature of 75C
was sprayed onto the TAED/STP rnixture using a WFM 504 jet at
3.5 kg/cm2. The resulting granules had a granulometry of about
90% (0.3-1.2 mm)g 0.5% (~ 1.2 mm) and 9.5% (~ 0.3 mm) and had
the following composition~
TAED 66.5%
Sodium triphosphate (expressed as anhydrous salt) 11.7%
Disodium orthophosphate (expressed as anhydrous salt~ 8.5%
Water 13.3%
These granules had excellent disintegration characteristics in
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the wash.
Second experiment
3.5 kg of the same TAED/STP mixture were placed in a 0.5 metre pan.
A solution containing 5.7% anhydrous sodium triphosphate and
37.5% disodium orthophosphate dihydrate was prepared. 0.75 kg of
this solution at a temperature of 75C was sprayed onto -the
TAED/STP mixture using a WFM 804 jet at 3.5 kg/cm2. The resulting
granules had a granulometry of 20.5% [~ 1.2 mm); 77% (1.2-0.3 mm)
and 2.5% (< 0.3 mm) and had the following composition: (Granule
Type II).
TAED 70 0%
sodium triphosphate (expressed as anhydrous salt) 13.4%
15 disodium orthophosphate (expressed as anhydrous salt) 5.3%
water 11. 3%
These granules were readily dispersed in the wash and had quite
satisfactory handling characteristics.
Storage trials were carried out with these granules for two and
four weeks' periods, at 37C/70% RH (relative humidity) in
laminated packets in a detergent base powder ~ to the following
composition: (A similar composition comprising unprotected TAED
25 was used as comparison)
% by weight
Detergent base powder ~ 81.0
TAED granules 8.0
30 Sodium perborate tetrahydrate 10.0
Proteolytic enzyme (Alcalase; 1.5 Anson Units) 1.0
The detergent base powder lS an anionic/nonionic binary active
powder based on sodium triphosphate.
The ~ollowing residual activities (%) were found:
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TAED perborate enzyme
2 weeks 4 weeks 2 weeks 4 weeks 2 weeks 4 weeks
Granule
Type I 94 89 102 77 69 60
5 Granule
Type II n/a 92 n/a 73 n/a 54
Unprotected
10 TAED n/a 44 n/a 43 n/a 16
Two principal tests were carried out to evaluate the utility of
the granules:
1) Granule strengt_
This was assessed by the use of the "Wallace Inden-tation Tester".
i5 This apparatus determines the crush-load in grams which is the
weight an individual granule will support. The apparatus is
operated simply by loading up the contacting plunger with
weights until the granule fails. An average is taken from
about 15 (but not less than 10) granules. In general it can be
said that a crush-load of above 20 grams is satisfactory.
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2) Granule disintegration
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This is estimated by placing 1 gram of the granules in 200 9
of distilled wa-ter at 25C in a beaker (diameter 7 cm). The
liquid is stirred with a flat-bladed (5 x 1~ cm) stirrer
- placed 4.2 cm above the base of the beaker. The stirrer speed
was 75-80 rpm. ~isual observatinn was used to estimate the
time taken for all granules to completely break up. A
satisfactory granule should have a maximum disintegration
time of 50 seconds.
The follo~1ng test results were obtained:
Disintegration time (in seconds) Crush !oad (in grams)
Granule I + 10 27
Granule II IS-20 ~ 55
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Example III
4.0 kg of a TAED/STP mixture containing 3400 g TAED, were placed
in a 0.5 metre granulating pan. A solution containing 47%
MgS04.7H20 was preferred. 2.2 kg of this solution, at a temperature
of 65-70 C, was sprayed onto the TAED/STP mixture using a WFM 804
jet at 3.5 kg/cm2. The resulting granules had a granulometry of
2.7% (> 1.2 mm); 84.2% (1.2-0.3 mm) and 13.1% (< 0.3 mm) and had
the following composition after weathering:
TAED 61.3%
Sodium triphosphate (anhydrous) 10.8%
Magnesium sulphate (anhydrous) 9.2%
Water 18.7%
The granules showed a disintegration time of 25-30 seconds and a
mean crush-load of 46 grams.
The following experiment was carried out, using sodium silicate
as the second hydrable salt.
4.0 kg of a TAED/STP mixture (3400 g TAED) in a granulating pan was
sprayed with 700 g of a solution containing 12.6% sodium triphosphate
and 19.1% sodium silicate (anhydrous) in the same way as in the
above Example. The silicate used was neutral silicate
(Na20 3.3 Si02)-
The resulting granules had a granulometry of 8.2% (' 1.2 mm);
81.2% (1.2-0.3 mm) and 10.6 (< 0.3 mm) and had the following
composition after weathering:
TAED 72.2%
Sodium triphosphate (anhydrous) 16.5%
Sodium silicate (anhydrous) 2.8%
Water 8.5%
Though the granules look all right and had a satisfactory crush-load
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oF 131 grams, they suffer from slow dissolving properties. The
measured disintegration time was ~ 120 seconds, which is
unsatisfactory.
Example IV
3400 grams oF pure TAED were mixed with 1000 grams of partially
dried borax decahydrate (- 1110 grams Na2B407.10H20) in a
granulating pan. A solution of 40% anhydrous disodium ortho-
phosphate was preparecl. 1.5 kg of this solution, at a temperature
oF 60~65C, was sprayed onto the TAED/borax mixture, using a
WFM 804 jet at 3~5kg/cm2. The resulting granules had a granulo-
metry of 0.8% ~> 1.2 mm); 78.3% (1.2-0.3 mm) and 20.9 (~ 0.3 mm),
and had the following composition:
rAED 60.5%
borax (anhydrous) 10.5%
DSOP (anhydrous) 10.7%
water 18.3%
Disintegration time was 20 seconds.
Mean crush-load was 25 grams.
For comparison granules were prepared without the use of a second
hydratable salt. The granules, which had the following composition:
TAED 69.0
Sodium triphosphate (anhydrous) 20.7
Water 10.3,
showed the following granule characteristics:
Crush-load 143 g.
disintegration time > 60 seconds
