Laundry bleaching composition

Dry bleaching compositions are disclosed which comprise an alkali metal salt of percarbonate and a dry-form composition comprising a carboxylic polymer. The compositions provide effective bleaching and are as stable upon manufacture and storage.

This application is a 371 of PCT/US93/04689 filed May 18, 1993. 
TECHNICAL FIELD 
The present invention relates to dry bleaching compositions for laundry. 
Dry laundry bleaching compositions are described which comprise 
percarbonate as the bleaching species, said compositions being stable upon 
manufacture and storage. 
BACKGROUND OF THE INVENTION 
The inorganic perhydrate bleach most widely used in the context of laundry 
bleaching is sodium perborate in the form of either the monohydrate or 
tetrahydrate. However, concerns about the impact of boron salts on the 
environment have led to an increasing interest in other perhydrate salts, 
of which sodium percarbonate is the most readily available. 
Detergent compositions containing sodium percarbonate are known in the art. 
Percarbonate salts, particularly sodium percarbonate, are attractive 
perhydrates for use in detergent compositions because they dissolve 
readily in water, are weight efficient and, after giving up their 
available oxygen, provide a useful source of carbonate ions for detergency 
purposes. 
However, the inclusion of percarbonate salts in detergent compositions has 
been restricted hitherto by the relative instability of the bleach both as 
is and in use. Sodium percarbonate loses its available oxygen at a 
significant rate in the presence of ions of heavy metals such as iron, 
copper and manganese and also in the presence of moisture, these effects 
being accelerated at temperatures in excess of about 30.degree. C. 
Moisture and heavy metal ions are unavoidable components of conventional 
granular laundry treatment compositions. Also percarbonate decomposition 
due to moisture becomes more of an issue during storage as laundry 
treatment products are often stored in humid environments where the 
product picks up moisture. This has resulted in marginally acceptable 
percarbonate bleach stability under Northern European summer conditions, 
where the average maximum temperature over the hottest months is from 
21.degree. C. to 25.degree. C., and unacceptable stability under 
temperatures higher than this. Such conditions are found in the Middle 
East and Southern Asia and also in Southern Europe where average maximum 
temperatures are in the 27.degree. C. to 33.degree. C. range for the 
hottest summer month. 
Such temperature accelerated percarbonate decomposition also occurs during 
the manufacture of the finished product. Indeed, as individual ingredients 
are mixed together the temperature of the mixture increases, accelerating 
the decomposition of the percarbonate. Furthermore, the temperature 
increase is greater if the mixing occurs under adiabatic or semi-adiabatic 
conditions. 
There has therefore been much activity by workers in the field to increase 
percarbonate stability so as to make it a viable component of detergent 
formulations. This activity has tended to concentrate on the protection of 
the percarbonate by coating the crystalline product or by inclusion of 
stabilizing agents during its manufacture, or both. Thus, while it has 
proved possible to incorporate percarbonate salts in conventional 
detergent compositions so as to have acceptable percarbonate stability 
over periods reflecting normal product shelf life, the percarbonate salts 
have proved complex and expensive to manufacture. This has restricted 
their broadscale utilization, as evidenced by the relatively small number 
of commercially available products containing percarbonate. 
It is therefore an object of the present invention to provide a dry laundry 
bleaching composition incorporating an alkali metal percarbonate bleach, 
said bleach displaying improved stability both upon the manufacture and 
the storage of said dry laundry bleaching composition. 
It is a further object of the present invention to provide a dry laundry 
bleaching composition incorporating an alkali metal percarbonate bleach 
displaying improved stability, in which the percarbonate bleach does not 
require complex protection techniques. 
It has now been found that these objects could be met by formulating a 
composition comprising an alkali metal salt of percarbonate together with 
a dry-form composition comprising a polymer, as described hereinafter. 
Dry bleaching compositions comprising percarbonate have been described for 
instance in FR 2,385,837, U.S. Pat. No. 4,428,914, GB 1,553,505 and J 
4001299 (abstract). Polymers such as those used in the contest of the 
present invention have been described for instance in EP 137 669. 
The compositions according to the present invention also allow adequate 
control of the pH in the bleaching liquor, giving appropriate balance 
between bleaching performance and fabric safety. 
SUMMARY OF THE INVENTION 
Compositions according to the present invention are dry bleaching 
compositions comprising from about 10% to about 80% by weight of the total 
composition of an alkali metal salt of percarbonate bleach and from 0.1% 
to 50% by weight of the total composition of a dry-form composition 
comprising at least 50% by weight of said dry-form composition of a 
polymer according to formula I: 
##STR1## 
wherein Y is a comonomer or comonomer mixture; R.sup.1 and R.sup.2 are 
bleach- and alkali-stable polymer-end groups; R.sup.3 is H, OH or 
C.sub.1-4 alkyl; M is H, alkali metal, alkaline earth metal, ammonium or 
substituted ammonium; p is from 0 to 2; and n is at least 10, or mixtures 
thereof. 
DETAILED DESCRIPTION OF THE INVENTION 
The percarbonate: 
As a first essential component, the compositions according to the present 
invention comprise an alkali metal salt of percarbonate, preferably sodium 
percarbonate. Sodium percarbonate is available commercially as a 
crystalline solid. Most commercially available material includes a low 
level of a heavy metal sequestrant such as EDTA, 1-hydroxyethylidene 
1,1-diphosphonic acid (HEDP) or an amino-phosphonate, that is incorporated 
during the manufacturing process. For the purposes of the present 
invention, the percarbonate can be incorporated into detergent 
compositions without additional protection. 
Whilst heavy metals present in the sodium carbonate used to manufacture the 
percarbonate can be controlled by the inclusion of sequestrants in the 
reaction mixture, it is preferred that the percarbonate be protected from 
heavy metals present as impurities in other ingredients of the product. It 
has been found that the total level of Iron, Copper and Manganese ions in 
the product should not exceed 25 ppm and preferably should be less than 20 
ppm in order to avoid an unacceptably adverse effect on percarbonate 
stability. 
The compositions according to the present invention comprise from 10% to 
80% by weight of the total composition of percarbonate, preferably from 
40% to 50%. In other words, in terms of percarbonate activity, the 
compositions according to the present invention comprise from about 1.5% 
to about 11% available oxygen, preferably from about 5.6% to 7%. 
The dry-form composition: 
The second essential component of the invention is a dry-form composition 
comprising at least 50% by weight of said dry-form composition of a 
polymer according to formula I: 
##STR2## 
wherein Y is a comonomer or comonomer mixture; R.sup.1 and R.sup.2 are 
bleach- and alkali-stable polymer-end groups; R.sup.3 is H, OH or 
C.sub.1-4 alkyl; M is H, alkali metal, alkaline earth metal, ammonium or 
substituted ammonium; p is from 0 to 2; and n is at least 10, or mixtures 
thereof. 
Preferred polymers for use herein fall into two categories. The first 
category belongs to the class of copolymeric polymers which are formed 
from an unsaturated polycarboxylic acid such as maleic acid, citraconic 
acid, itaconic acid, mesaconic acid and salts thereof as first monomer, 
and an unsaturated monocarboxylic acid such as acrylic acid or an alpha 
--C.sub.1-4 alkyl acrylic acid as second monomer. Referring to formula I 
hereinabove, the polymers belonging to said first class are those where p 
is not 0 and Y is selected from the acids listed hereinabove. Preferred 
polymers of this class are those according to formula I hereinabove, where 
Y is maleic acid. Also, in a preferred embodiment, R.sub.3 and M are H, 
and n is such that the polymers have a molecular weight of from 1000 to 
400 000 atomic mass units. 
The second category of preferred polymers for use herein belongs to the 
class of polymers in which, referring to formula I hereinabove, p is 0 and 
R.sup.3 is H or C.sub.1-4 alkyl. In a preferred embodiment, n is such that 
the polymers have a molecular weight of from 1000 to 400000 atomic mass 
units. In a highly preferred embodiment, R.sub.3 and M are H. 
The alkali-stable polymer end groups R.sub.1 and R.sub.2 in formula I 
hereinabove suitably include alkyl groups, oxyalkyl groups and alkyl 
carboxylic acid groups and salts and esters thereof. 
In the above, n, the degree of polymerization of the polymer can be 
determined from the weight average polymer molecular weight by dividing 
the latter by the average monomer molecular weight. Thus, for a 
maleic-acrylic copolymer having a weight average molecular weight of 
15,500 and comprising 30 mole % of maleic acid derived units, n is 182 
(i.e. 15,500/(116.times.0.3+72.times.0.7). 
In case of doubt, weight-average polymer molecular weights can be 
determined herein by gel permeation chromatography using Water mu! 
Porasil.RTM. GPC 60 A.sup.2 and mu! Bondagel.RTM. E-125, E-500 and E-1000 
in series, temperature-controlled columns at 40.degree. C. against sodium 
polystyrene sulphonate polymer standards, available from Polymer 
Laboratories Ltd., Shropshire, UK, the polymer standards being 0.15M 
sodium dihydrogen phosphate and 0.02M tetramethyl ammonium hydroxide at pH 
7.0 in 80/20 water/acetonitrile. 
Of all the above, highly preferred polymers for use herein are those of the 
first category in which n averages from 100 to 800, preferably from 120 to 
400. 
The dry-form compositions to be used herein comprise at least 50% by weight 
of said dry-form composition of a polymer as described hereinbefore, 
preferably at least 70%, most preferably at least 85%. By "dry", it is 
meant herein that said dry-form composition comprising said polymer is 
substantially free of water. Several such dry-form compositions are 
commercially available, for instance SOKALAN.RTM. DCP45, CP5, CP7 and 0 
from BASF, and NORASOL SP02ND.RTM. from NORSOHAAS. 
The dry bleaching compositions according to the present invention comprise 
from about 0.1% to about 50% by weight of the total composition of said 
dry-form composition, preferably from about 1% to about 10%, most 
preferably from about 1.5% to about 6%. 
Optional ingredients: 
As an optional but highly preferred component, the compositions according 
to the present invention further comprise acidifying agent or mixtures 
thereof. The purpose of said acidifying agent is to control the alkalinity 
generated by the percarbonate in the bleaching liquor. Said agent is 
preferably incorporated in the product in an anhydrous form, and to have a 
good stability in oxidizing environment. Suitable anhydrous acidifying 
agents for use herein are carboxylic acids such as citric acid, succinic 
acid, adipic acid, glutaric acid, 3 ketoglutaric acid, citramalic acid, 
tartaric acid and maleic acid. Other suitable acidifying agents include 
sodium bicarbonate, and silicic acid. Highly preferred for use herein is 
anhydrous citric acid. Indeed, citric acid is commercially available in 
anhydrous form, it additionally acts as a builder and a chelant, and it is 
biodegradable. The compositions according to the present invention 
comprise from up to 15% by weight of the total composition of anhydrous 
citric acid, preferably from 2% to 8%, most preferably about 5%. 
Also optional but highly preferred ingredients are peroxy carboxylic acids 
bleach or precursors thereof, commonly referred to as bleach activators, 
which are preferably added in a prilled or agglomerated form. Examples of 
suitable compounds of this type are disclosed in British Patent GB 1 586 
769 and GB 2 143 231 and a method for their formation into a prilled form 
is described in European Published Patent Application EP-A-62 523. 
Preferred examples of such compounds are tetracetyl ethylene diamine 
(TAED), sodium 3, 5, 5 trimethyl hexanoyloxybenzene sulphonate, diperoxy 
dodecanoic acid as described for instance in U.S. Pat. No. 4,818,425 and 
nonylamide of peroxyadipic acid as described for instance in U.S. Pat. No. 
4,259,201 and n-nonanoyloxybenzenesulphonate (NOBS), and acetyl triethyl 
citrate (ATC) such as described in European Patent application 91870207.7. 
Compositions in accordance with the invention can also comprise other 
optional ingredients such as builder, optical brighteners, anti dusting 
agents such as olefines and waxes, enzymes, chelants, dispersants, dye 
transfer inhibition systems, surfactants, soil release agents, 
photoactivated bleaches such as Zn phthalocyanine sulphonate, dyes, 
pigments and perfumes are examples of such optional ingredients and can be 
added in varying amounts as desired. 
The compositions according to the present invention naturally comprise 
inorganic filler salts such as alkali metal carbonates, bicarbonates and 
sulphates. Such fillers, for instance sodium bicarbonate, may also act as 
acidifying agent as described herein above. Accordingly, sodium 
bicarbonate is a preferred filler material for use herein. 
The compositions according to the present invention can be made by a 
variety of methods well known in the art, including dry-mixing, spray 
drying, coating, agglomeration and granulation and combinations thereof. 
The compositions according to the present invention can be prepared with 
different bulk densities, from conventional granular products to so-called 
"concentrated" products (i.e. with a bulk density above 600 g/l).