Title of Invention	COATED SODIUM PERCARBONATE PARTICLES PROCESS FOR THEIR PREPARATION THEIR USE IN DETERGENT COMPOSITIONS AND DETERGENT COMPOSITIONS CONTAINING THEM
Abstract	Coated sodium percarbonate particles containing: a) a sodium percarbonate core, and b) a coating layer substantially free from sulphate, borate and magnesium compounds, comprising at least 30 and at most 75 % w/w of an alkali metal carbonate and at least 25 and at most 70 % w/w of an alkali metal silicate, the alkali metal carbonate and silicate being uniformly dispersed in the coating layer. Process for the preparation of the coated

Title of Invention

COATED SODIUM PERCARBONATE PARTICLES PROCESS FOR THEIR PREPARATION THEIR USE IN DETERGENT COMPOSITIONS AND DETERGENT COMPOSITIONS CONTAINING THEM

Abstract

Coated sodium percarbonate particles containing: a) a sodium percarbonate core, and b) a coating layer substantially free from sulphate, borate and magnesium compounds, comprising at least 30 and at most 75 % w/w of an alkali metal carbonate and at least 25 and at most 70 % w/w of an alkali metal silicate, the alkali metal carbonate and silicate being uniformly dispersed in the coating layer. Process for the preparation of the coated

Full Text	FORM 2 THE PATENTS ACT 1970 [39 OF 1970] COMPLETE SPECIFICATION [See Section 10] "COATED SODIUM PERCARBONATE PARTICLES, PROCESS FOR THEIR PREPARATION, THEIR USE IN DETERGENT COMPOSITIONS AND DETERGENT COMPOSITIONS CONTAINING THEM" SOLVAY [SOCIETE ANONYME], a Belgian company, of 33, Rue du Prince Albert, B-1050 Brussels, Belgium, The following specification particularly describes the nature of the invention and the manner in which it is to be performed:- 24-06-2004 Coated sodium percarbonate particles, process for their preparation, their use in detergent compositions and detergent compositions containing them The present invention is related to coated sodium percarbonate particles, to a process for the preparation of the coated sodium percarbonate particles, to the use of the coated sodium percarbonate particles in detergent compositions and to detergent compositions comprising the coated sodium percarbonate particles. 5 The use of sodium percarbonate (or sodium carbonate peroxyhydrate) as the active bleach constituent in detergent compositions for household fabric washing or dish washing is well known. Commonly such detergent compositions contain among other components zeolites as builder material, enzymes, bleach activators and/or perfumes. However, the interaction between sodium 10 percarbonate and other formulation components leads to progressive decomposition of the percarbonate and hence to loss of bleaching power during storage and transportation of the composition. A number of proposals have been made to overcome this problem by interposing a layer between the sodium percarbonate and its environment, called a coating layer. For instance in the 15 Belgian patent BE 842014 sodium sulphate is used as one of the constituents of the coating layer. In the international patent application WO 96/14389 a magnesium salt is used as one of the constituents of the coating layer. In the patent application JP 59/204697 a borate is used as one of the constituents of the coating layer. These known coating layers do not result in an optimum 20 combination of properties since they do not confer simultaneously a good stability to the sodium percarbonate when present in the detergent composition, a rapid dissolution rate when the composition is used in washing applications and a low moisture affinity when the composition is stored at high humidity. The aim of the present invention is to overcome the aforementioned 25 drawback by proposing new coated sodium percarbonate particles presenting simultaneously a good stability, a rapid dissolution rate and a low moisture affinity. Consequently, the invention concerns coated sodium percarbonate particles containing: 30 a) a sodium percarbonate core, and 2 b) a coating layer substantially free from sulphate, borate and magnesium compounds, comprising at least 30 and at most 75 % w/w of an alkali metal carbonate and at least 25 and at most 70 % w/w of an alkali metal silicate, the alkali metal carbonate and silicate being uniformly dispersed in the coating 5 layer. By substantially free from sulphate, borate and magnesium compounds is meant less than 5 % w/w of the total coating, preferably less than 2 % w/w of the total coating, more preferably less than 1 % w/w of the total coating, most preferably less than 0,5 % w/w of the total coating, of sulphate, borate and/or 10 magnesium compounds. In a preferred embodiment, the coating layer contains only the alkali metal carbonate and silicate. One of the essential characteristics of the invention resides in the combination of an alkali metal carbonate with an alkali metal silicate in the 15 coating layer in the given proportions and the substantial absence of sulphate, borate and magnesium compounds in the coating layer. It has indeed been found that this combination confers advantageous properties to the sodium percarbonate which become clear in the following paragraphs. Another important element of the invention resides in the uniform 20 distribution of the alkali metal carbonate and silicate in the coating layer. This means that it is not possible to determine within the coating layer the presence of parts which contain solely alkali metal carbonate and/or parts which contain solely alkali metal silicate. In other words, the carbonate and the silicate have been applied together to the sodium percarbonate core as a uniform mixture so that 25 they are equally dispersed on the surface of the core particles and that the coating layer comprises a homogeneous mixture of carbonate and silicate. The coating layer of the coated sodium percarbonate according to the invention comprises preferably at leaj^0_% w/wjDf alkali metal carbonate. Advantageously it comprises at most 70 %„wiw of alkali metal carbonate. 30 Preferably it comprises at least30JVwiw of alkali metal silicate. Advantageously it comprises at mostJ>£L% w^w °f alkali metal silicate. Coating layers comprising from 40 to 70 % w/w of alkali metal carbonate and from 30 to 60 % w/w of alkali metal silicate are convenient. It has been observed that low levels of alkali metal carbonate are not desirable because the tackiness of these systems facilitate 35 agglomeration of the coated particles which is undesirable. 3 Preferably, sodium carbonate and sodium silicate are used as the alkali metal carbonate and silicate. In the coated sodium percarbonate particles according to the invention the fraction of the coating layer is usually at least 1 % w/w. It is in particular at least 5 2 % w/w. The fraction of coating layer is commonly at most 5 % w/w. More particularly it is at most 4 % w/w. Fractions of coating layer from 1 to 5 % w/w of the coated sodium percarbonate, preferably from 2 to 4 % w/w are convenient. Fractions of coating layer superior to 5 % lead to lowering of Avox and are difficult to achieve in a single coating operation without significant product 10 agglomeration. The coated sodium percarbonate particles according to the invention present usually an Avox of at least 12 % w/w. The Avox is preferably at least 13,9 % w/w. The Avox is generally at most 15 % w/w. It is in particular at most 14,6 % w/w, Avox values from 12 to 15 % w/w and preferably from 13,9 to 15 14,4 % w/w are convenient. The highest Avox values are obtained when the coating layer contains at least 50 % w/w of alkali metal carbonate. The Avox is the available oxygen found in sodium percarbonate and indicates the amount of oxygen utilisable in a chemical reaction. It is measured by titration with potassium permanganate after dissolution in sulfuric acid (see ISO 1917-1982) according to 20 the following reaction : The coated sodium percarbonate particles according to the invention usually 25 have a bulk density of at least 0,9 g/cm3. The bulk density is preferably at least 1,0 g/cm3. It is generally at most 1,2 g/cm3. It is in particular at most 1,1 g/cm3. Bulk densities from 0,9 to 1,2 g/cm3, preferably from 1,0 to 1,1 g/cm3 give good results. The bulk density is measured by recording the mass of sample in a stainless steel cylinder of internal height and diameter of 86.1 mm, after running 30 the sample out of a funnel (upper internal diameter 108 mm, lower internal diameter 40 mm, height 130 mm) placed 50 mm directly above the receiver. The higher levels of alkali metal carbonate in the coating layer ensure that a high bulk density is achieved. The coated sodium percarbonate particles according to the invention 35 present usually a low rate at which it picks up moisture from a humid atmosphere. The capability to pick up moisture is measured by the following test: a 9 cm 4 diameter petri dish with a 1 cm depth rim is weighed accurately on a 4 decimal place balance (Wl). A sample of dry coated sodium percarbonate (about 20 g) is placed on the petri dish which is gently agitated to generate an even particulate layer across the base of the dish and reweighed on the same balance (W2). The 5 sample on the petri dish is stored in a room, about 3 m high, wide and long in an atmosphere maintained for a period of 24 hours at 32 °C by a thermostat controlled heater and at 80 % Relative Humidity (RH) by introduction of a fine droplet water spray under the control of a humidity detector and weighed on the same balance (W3). The samples are protected by a shield from the spray. The 10 moisture pick-up of the coated sodium percarbonate is calculated as follows : Moisture Pick-up (g/kg) = 1000 x (W3 - W2) (W2-W1) The coated sodium percarbonate particles according to the invention have usually a moisture pick-up of at least 10 g/kg. It is in particular at least 15 g/kg. 15 More specifically it is at least 20 g/kg. The moisture pick-up is generally at most 100 g/kg. Preferably it is at most 70 g/kg. More preferably it is at most 50 g/kg. Moisture pick-up values from 10 to 100 g/kg, preferably from 15 to 70 g/kg, and most preferably from 20 to 50 g/kg give good results. It has been observed that high levels of alkali metal carbonate in the coating layer lead to low moisture 20 affinity. The coated sodium percarbonate particles according to the invention have usually a 90 % dissolution time of at least 0,5 min. It is in particular at least 0,9 min. Generally the 90 % dissolution time is at most 3 min. It is preferably at most 2,5 min. 90 % dissolution times from 0,5 to 3 min, preferably from 0,9 to 25 2,5 min give good results. The 90 % dissolution time is the time taken for conductivity to achieve 90 % of its final value after addition of coated sodium percarbonate to water at 15°C and 2 g/1 concentration. The method used is adapted from ISO 3123-1976 for industrial perborates, the only differences being the stirrer height that is 1 mm from the beaker bottom and a 2 litre beaker 30 (internal height 183 mm, internal diameter 127 mm). High levels of alkali metal carbonate in the coating layer, preferably at least 70 % w/w, lead to rapid dissolution which is desirable. This is however not the case when highly alkaline silicate sources are used during coating e.g. where the SiC2/Na20 molar ratio is 1,0 or less. In this case the high alkalinity ensures rapid dissolution. 35 The coated sodium percarbonate particles according to the invention usually have an attrition measured according to the ISO standard method 5937-1980 of at least 0,05 %. The attrition is in particular at least 0,1 %. Attrition values of at most 5 % are usual. Values of at most 4 % are preferred. Attrition values from 0,05 to 5 %, preferably from 0,1 to 4 % are convenient. The coated sodium percarbonate particles according to the invention usually 5 present a thermal stability, measured using microcalorimetry at 40°C, of at least 0,1 uW/g. The thermal stability is advantageously at least 0,2 uW/g. It is most preferably at least 0,3 uW/g. It is generally at most 12 uW/g. More particularly, it is at most 4 uW/g. Values of at most 3 uW/g give the best results. Thermal stabilities from 0,1 to 12 uW/g, preferably from 0,2 to 4 uW/g, most preferably 10 from 0,3 to 3 uW/g, give good results. The measurement of thermal stability consists of using the heat flow or heat leakage principle using a LKB 2277 Bio Activity Monitor. The heat flow between an ampule containing the coated sodium percarbonate and a temperature controlled water bath is measured and compared to a reference material with a known heat of reaction. 15 The coated sodium percarbonate particles according to the invention usually present a mean particle size of at least 500 um. The mean particle size is advantageously at least-550 urn. It is generally at most 900 um. Preferably it is at most 850 um. Mean particle sizes from 500 to 900 um, preferably from 550 to 850 um give good results. 20 The coated sodium percarbonate particles according to the invention usually present a specific surface area of at least 2 m^/kg. It is in particular at least 3 nfi/kg. The specific surface area is generally at most 6 m^/kg. It is preferably at most 5,3 m^/kg. Specific surface areas from 2 to 6 m^/kg, preferably from 3 to 5,3 m^/kg give particularly good results. The specific surface area for sodium 25 percarbonate is calculated from sieve analysis using a minimum of 5 sieves on the basis of the following formula : Specific surface area per unit mass wj = the weight fraction of particles in fraction i, dj = the particle density of sodium percarbonate (2140 kg/m3), 30 r[ = the mean radius of particles in fraction i. The calculation assumes approximately spherical, non-porous particles. The coated sodium percarbonate particles according to the invention usually contain a fraction of particles having a particle size superior to 1000 um of at most 30 % w/w. It is preferably at most 20 % w/w. Large fractions above 35 1000 um give rise to unwanted segregation of bleach from a detergent matrix on 6 handling and can have an undesirable appearance. The fraction of particles having a particle size superior to 1000 urn is usually at least 0,1 % w/w. The sodium percarbonate core can be obtained for example by crystallisation from a bulk saturated solution of sodium percarbonate in a 5 crystalliser/classifier. Preferably, the sodium percarbonate core is obtained using a crystallisation process without salting-out agent. For instance, the crystallisation process described in the international patent application WO 97/01562 of SOLVAYINTEROX, the entire specification of which is incorporated herein by reference, is particularly useful for obtaining such sodium percarbonate core 10 particles. Other sodium percarbonate core particles that are particularly useful as core particles of the invention are those described in the international patent application WO 97/35951 of SOLVAY INTEROX the entire specification of which is incorporated herein by reference. The coating layer can optionally contain other constituents. 15 The coated sodium percarbonate according to the invention can be prepared by any known coating process adapted to this purpose. A particularly performant coating process consists in introducing into a mixer uncoated sodium percarbonate core particles and a coating solution obtained by mixing an alkali metal carbonate solution and an alkali metal silicate solution, operating the mixer 20 at a temperature from room temperature to 50 °C in order to distribute the coating solution on the surface of the core particles and to obtain wet coated particles, removing the wet coated particles from the mixer and drying them in a fluid bed dryer using a stream of hot air of a temperature from 50 to 90°C in order to obtain dry coated particles. 25 Consequently, the present invention also concerns this process. In the process according to the invention it can be interesting to operate the mixer at a temperature higher than room temperature in order to maintain the stability of the coating solution and to avoid that the coating constituents crystallise too soon before they are brought into contact with the surface of the 30 sodium percarbonate core particles. This is especially the case when highly alkaline silicate solutions are used. It is recommended not to use the mother liquor from the crystallisation process as coating solution in the process according to the invention. In the process according to the invention chelating agents can be added to 35 the mixer. These agents can assure chelation of the transition~metal ion impurities^ which are responsible for the decomposition of the sodium percarbonate. Suitable ~7 chelating agents can be selected from polycarboxylate or polyphosphonate salts, as such or in acid form. Examples are polyaminocarboxylates such as EDTA or DTP A, polyaminomethylenephosphonates such as EDTMPA, CDTMPA and DTPMPA and hydroxyalkylenephosphonates such as hydroxyethylidenediphos-5 phonate. A convenient amount of chelating agent"is often selected from 0,5 to 20 g/kg sodium percarbonate. The silicate solution used in the process according to the invention are usually characterised by their molar ratio SiO2/Na20. This ratio is advantageously at least 1. It is preferably at least 2. Good results have been 10 obtained with molar ratios of up to 4. The best results are obtained with ratios up to 3,3. Molar ratios from 1 to 4 and in particular from 2 to 3,3 are convenient. This molar ratio can be controlled by adding more or less alkaline source for instance NaOH. The coating solutions used in the process according to the invention usually 15 contain at least 20 % w/w of total amount of coating agent (alkali metal silicate and alkali metal carbonate and optionally other agents). Most often it contains at least 25 % w/w of coating agent. This amount is generally at most 50 % w/w. Amounts of at most 35 % w/w are convenient. Amounts of around 30 % w/w are preferred. Amounts from 20 to 50 % w/w, in particular from 25 to 30 % w/w are 20 convenient. The wet coated particles removed from the mixer advantageously contain 4 to 10 % w/w of moisture, advantageously 5 to 8 w/w of moisture. The dried coated particles preferably contain from 0,2 to 0,6 % w/w of moisture. The coated sodium percarbonate particles according to the invention can 25 advantageously be used as active bleach constituent in detergent compositions. The present invention therefore concerns also the use of the above described coated sodium percarbonate particles as active bleach constituent in detergent compositions. The present invention also concerns detergent compositions containing the 30 above described coated sodium percarbonate particles as active bleach constituent and a builder, either zeolitic or non-zeolitic. The detergent compositions can also contain other constituents such as surfactants, anti-redeposition and soil suspension agents, bleach activators, optical brightening agents, soil release agents, suds controllers, enzymes, fabric softening agents, perfumes, colours and 35 processing aids. The incorporation of coated percarbonate into detergent 8 powders or granules with a bulk density of 0,4 to 1,0 g/cm^ and into detergent tablets which are either zeolite or phosphate built is particularly advantageous. Example Sodium percarbonate was manufactured using the continuous aqueous 5 crystallisation process free from sodium chloride described in the international patent application WO 97/35806. From this process material with the following properties was generated : Avox = 14,61 % w/w Bulk density = 1,03 g/cm^ 10 Moisture pick-up = 6 g/kg 90 % dissolution time = 0,9 min Attrition = 1,5% Thermal stability =1,7 uW/g Mean particle size = 779 urn. 15 1 kg of this product was placed in a ploughshare mixer operating at around 150 rpm. To the sodium percarbonate was added 103,1 g of a coating solution containing: 200 g/kg anhydrous sodium carbonate, 206,2 g/kg sodium silicate solution which was a 48,5 w/w solids amorphous 20 sodium silicate solution with a SiO2/Na20 molar ratio of 2,0, 593,8 g/kg demineralised water. The coating solution with 30 % w/w solids was added over a 2 min period, with a further 3 min mixing. The wet product was then discharged into a fluid bed dryer and fluid bed dried in air for 30 min with a bed temperature of 70°C. The 25 characteristics of the coated sodium percarbonate after treatment was as follows : Coating : 3 % w/w total Coating composition : 67 % sodium carbonate, 33 % sodium silicate Avox = 14,01 % w/w Bulk density = 1,05 g/cm3 3 0 Moisture pick-up = 41,3 g/kg 90 % dissolution time = 2,2 min Attrition = 1,1 % Thermal stability = 2,5 uW/g Mean particle size = 772 um 3 5 Calculated specific surface area = 4,0 m2/kg Fraction of material above 1000 um = 16 % w/w In order to assess the effectiveness of the coated sodium percarbonate, two detergent formulations were made by blending coated or uncoated sodium percarbonate with a zeolite 4A built detergent to give the following compositions: 5 Sodium linear alkyl benzene sulphonate = 8,3 % w/w Ethoxylated tallow alcohol - 4,4 % w/w Soap = 3,1 % w/w Zeolite 4A = 27,6 % w/w Sodium carbonate = 10,0 % w/w 10 Sodium acrylate/maleate copolymer = 4,4 % w/w 3,3 molar ratio SiO2/Na20 sodium silicate = 2,9 % w/w Carboxymethylcellulose = 0,2 % w/w Sodium EDTA = 0,.2% w/w Optical brightening agent = 0,2 % w/w 15 Sodium sulphate = 6,3 % w/w Moisture = 10,4 % w/w Coated or uncoated sodium percarbonate = 15,0 % w/w The 2 formulations generated were stored in sealed polyethylene coated cardboard cartons at 32°C and 80 % RH for a period of 6 weeks. The Avox was 20 monitored using potassium permanganate titration during this stability trial. The following results were generated : Sodium percarbonate % Avox recovery = Avox after x weeks x 100 initial Avox x = 2 x = 4 x=6 uncoated 70 51 43 coated • 78 65 53 The effectiveness of the coated percarbonate was also assessed by blending coated or uncoated sodium percarbonate with a sodium tripolyphosphate built detergent to give the following compositions : 25 Sodium linear alkyl benzene sulphonate = 6,8 % w/w Ethoxylated tallow alcohol = 2,5 % w/w Soap = 3,0 % w/w Sodium tripolyphosphate = 37,2 % w/w 3,3 molar ratio SiO2/Na20 sodium silicate = 6,4 % w/w 30 Magnesium silicate = 1,6 % w/w Carboxymethylcellulose = 1,0 % w/w WE CLAIM: 1. Coated sodium percarbonate particles containing: a) a sodium percarbonate core, and b) a coating layer comprising at least 40 and at most 70 % w/w of an alkali metal carbonate, at least 30 and at most 60 % w/w of an alkali metal silicate,! less than 5 % w/w of the total coating of sulphate, borate and magnesium compound sjthe coating layer being obtained by using the alkali metal carbonate and silicate simultaneously in the form of a coating solution in order to obtain a uniform dispersion of the alkali metal carbonate and alkali metal silicate carbonate in the coating layer A and the fraction of coating layer being from 1 to 5 % w/w of the coated sodium percarbonate. "I 2. Coated sodium percarbonate particles as claimed in claim 1 presenting an Avox of the kind as herein described from 12 to 15% w/w, a bulk density from 0.9 to 1.2 g/cm3, and a moisture pick-up from 10 to 100 g/kg. \3y Coated sodium percarbonate particles as claimed in claim 2 presenting the Avox from 13.9 to 14.4% w/w, a bulk density from 1.0 to 1.1 g/Cm3 and a moisture pick-up from 15 to 70 g/kg. 4. Coated sodium percarbonate particles as claimed in any one of claims 1 to 3 presenting a 90 % dissolution time from 0.5 to 3 min, preferably from 0.9 to 2.5 min, an attrition, measured according to the ISO standard method 5937-1980, from 0.05 to 5%, preferably from 0.1 to 4%, and a thermal stability, measured using microcalorimetry at 40°C, from 0.1 to 12 p.W/g, in particular from 0.2 to 4 W/g, preferably from 0.3 to 3 nW/g. 5. Coated sodium percarbonate particles as claimed in any one of claims 1 to 4 presenting a mean particle size from 500 to 900 \|.im, preferably from 550 to 850 \|u.m, a surface area from 2 to 6 m2/kg, preferably from 3 to -12- 5.3 m2/kg, and containing a fraction of particles having a particle size superior to 1000 \|j.m of at most 30 % w/w, preferably at most 20 % w/w. 6. Coated sodium percarbonate particles as claimed in any one of claims 1 to 5 wherein the sodium percarbonate core is obtained using a crystallisation process without salting-out agent. 7. Process for preparing the coated sodium percarbonate particles as claimed in any one of claims 1 to 6 in which uncoated sodium percarbonate core particles and a coating solution obtained by mixing an alkali metal carbonate solution and an alkali metal silicate solution are introduced into a mixer, the mixer is operated at a temperature from room temperature to 50°C in order to distribute the coating solution on the surface of the core particles and to obtain wet coated particles, the wet coated particles are removed from the mixer and dried in a fluid bed dryer using a stream of hot air of a temperature from 50 to 90°C in order to obtain dry coated particles. 8. Process as claimed in claim 7 wherein the alkali metal silicate solution is a sodium silicate solution presenting a molar ratio Si02/Na20 from 1 to 4, preferably from 2 to 3.3. 9. Detergent compositions containing the coated sodium percarbonate particles as claimed in any one of claims 1 to 6 as active bleach constituent and a zeolitic builder. 10. Detergent compositions containing the coated sodium percarbonate particles as claimed in any one of claims 1 to 6 as active bleach constituent and a non- zeolitic builder. Dated this 30TH day of November, 2000 {NALINI KRISHNAMURT]) OF REMFRY & SAGAR ATTORNEY FOR THE APPLICANTS -13-

Full Text

FORM 2
THE PATENTS ACT 1970 [39 OF 1970]
COMPLETE SPECIFICATION
[See Section 10]
"COATED SODIUM PERCARBONATE PARTICLES, PROCESS FOR THEIR PREPARATION, THEIR USE IN DETERGENT COMPOSITIONS AND DETERGENT COMPOSITIONS CONTAINING THEM"
SOLVAY [SOCIETE ANONYME], a Belgian company, of 33, Rue du Prince Albert, B-1050 Brussels, Belgium,
The following specification particularly describes the nature of the invention and the manner in which it is to be performed:-

24-06-2004

Coated sodium percarbonate particles, process for their preparation, their use in detergent compositions and detergent compositions containing them
The present invention is related to coated sodium percarbonate particles, to
a process for the preparation of the coated sodium percarbonate particles, to the
use of the coated sodium percarbonate particles in detergent compositions and to
detergent compositions comprising the coated sodium percarbonate particles.
5 The use of sodium percarbonate (or sodium carbonate peroxyhydrate) as
the active bleach constituent in detergent compositions for household fabric washing or dish washing is well known. Commonly such detergent compositions contain among other components zeolites as builder material, enzymes, bleach activators and/or perfumes. However, the interaction between sodium
10 percarbonate and other formulation components leads to progressive
decomposition of the percarbonate and hence to loss of bleaching power during storage and transportation of the composition. A number of proposals have been made to overcome this problem by interposing a layer between the sodium percarbonate and its environment, called a coating layer. For instance in the
15 Belgian patent BE 842014 sodium sulphate is used as one of the constituents of the coating layer. In the international patent application WO 96/14389 a magnesium salt is used as one of the constituents of the coating layer. In the patent application JP 59/204697 a borate is used as one of the constituents of the coating layer. These known coating layers do not result in an optimum
20 combination of properties since they do not confer simultaneously a good stability to the sodium percarbonate when present in the detergent composition, a rapid dissolution rate when the composition is used in washing applications and a low moisture affinity when the composition is stored at high humidity.
The aim of the present invention is to overcome the aforementioned
25 drawback by proposing new coated sodium percarbonate particles presenting simultaneously a good stability, a rapid dissolution rate and a low moisture affinity.
Consequently, the invention concerns coated sodium percarbonate particles containing:
30 a) a sodium percarbonate core, and
2

b) a coating layer substantially free from sulphate, borate and magnesium
compounds, comprising at least 30 and at most 75 % w/w of an alkali metal
carbonate and at least 25 and at most 70 % w/w of an alkali metal silicate, the
alkali metal carbonate and silicate being uniformly dispersed in the coating
5 layer.
By substantially free from sulphate, borate and magnesium compounds is meant less than 5 % w/w of the total coating, preferably less than 2 % w/w of the total coating, more preferably less than 1 % w/w of the total coating, most preferably less than 0,5 % w/w of the total coating, of sulphate, borate and/or 10 magnesium compounds.
In a preferred embodiment, the coating layer contains only the alkali metal carbonate and silicate.
One of the essential characteristics of the invention resides in the combination of an alkali metal carbonate with an alkali metal silicate in the 15 coating layer in the given proportions and the substantial absence of sulphate, borate and magnesium compounds in the coating layer. It has indeed been found that this combination confers advantageous properties to the sodium percarbonate which become clear in the following paragraphs.
Another important element of the invention resides in the uniform 20 distribution of the alkali metal carbonate and silicate in the coating layer. This
means that it is not possible to determine within the coating layer the presence of parts which contain solely alkali metal carbonate and/or parts which contain solely alkali metal silicate. In other words, the carbonate and the silicate have been applied together to the sodium percarbonate core as a uniform mixture so that 25 they are equally dispersed on the surface of the core particles and that the coating layer comprises a homogeneous mixture of carbonate and silicate.
The coating layer of the coated sodium percarbonate according to the invention comprises preferably at leaj^0_% w/wjDf alkali metal carbonate. Advantageously it comprises at most 70 %„wiw of alkali metal carbonate. 30 Preferably it comprises at least30JVwiw of alkali metal silicate. Advantageously it comprises at mostJ>£L% w^w °f alkali metal silicate. Coating layers comprising from 40 to 70 % w/w of alkali metal carbonate and from 30 to 60 % w/w of alkali metal silicate are convenient. It has been observed that low levels of alkali metal carbonate are not desirable because the tackiness of these systems facilitate 35 agglomeration of the coated particles which is undesirable.
3

Preferably, sodium carbonate and sodium silicate are used as the alkali metal carbonate and silicate.
In the coated sodium percarbonate particles according to the invention the fraction of the coating layer is usually at least 1 % w/w. It is in particular at least 5 2 % w/w. The fraction of coating layer is commonly at most 5 % w/w. More particularly it is at most 4 % w/w. Fractions of coating layer from 1 to 5 % w/w of the coated sodium percarbonate, preferably from 2 to 4 % w/w are convenient. Fractions of coating layer superior to 5 % lead to lowering of Avox and are difficult to achieve in a single coating operation without significant product 10 agglomeration.
The coated sodium percarbonate particles according to the invention present usually an Avox of at least 12 % w/w. The Avox is preferably at least 13,9 % w/w. The Avox is generally at most 15 % w/w. It is in particular at most 14,6 % w/w, Avox values from 12 to 15 % w/w and preferably from 13,9 to 15 14,4 % w/w are convenient. The highest Avox values are obtained when the coating layer contains at least 50 % w/w of alkali metal carbonate. The Avox is the available oxygen found in sodium percarbonate and indicates the amount of oxygen utilisable in a chemical reaction. It is measured by titration with potassium permanganate after dissolution in sulfuric acid (see ISO 1917-1982) according to 20 the following reaction :
The coated sodium percarbonate particles according to the invention usually 25 have a bulk density of at least 0,9 g/cm3. The bulk density is preferably at least 1,0 g/cm3. It is generally at most 1,2 g/cm3. It is in particular at most 1,1 g/cm3. Bulk densities from 0,9 to 1,2 g/cm3, preferably from 1,0 to 1,1 g/cm3 give good results. The bulk density is measured by recording the mass of sample in a stainless steel cylinder of internal height and diameter of 86.1 mm, after running 30 the sample out of a funnel (upper internal diameter 108 mm, lower internal
diameter 40 mm, height 130 mm) placed 50 mm directly above the receiver. The higher levels of alkali metal carbonate in the coating layer ensure that a high bulk density is achieved.
The coated sodium percarbonate particles according to the invention 35 present usually a low rate at which it picks up moisture from a humid atmosphere. The capability to pick up moisture is measured by the following test: a 9 cm
4

diameter petri dish with a 1 cm depth rim is weighed accurately on a 4 decimal place balance (Wl). A sample of dry coated sodium percarbonate (about 20 g) is placed on the petri dish which is gently agitated to generate an even particulate layer across the base of the dish and reweighed on the same balance (W2). The 5 sample on the petri dish is stored in a room, about 3 m high, wide and long in an atmosphere maintained for a period of 24 hours at 32 °C by a thermostat controlled heater and at 80 % Relative Humidity (RH) by introduction of a fine droplet water spray under the control of a humidity detector and weighed on the same balance (W3). The samples are protected by a shield from the spray. The
10 moisture pick-up of the coated sodium percarbonate is calculated as follows : Moisture Pick-up (g/kg) = 1000 x (W3 - W2)
(W2-W1) The coated sodium percarbonate particles according to the invention have usually a moisture pick-up of at least 10 g/kg. It is in particular at least 15 g/kg.
15 More specifically it is at least 20 g/kg. The moisture pick-up is generally at most 100 g/kg. Preferably it is at most 70 g/kg. More preferably it is at most 50 g/kg. Moisture pick-up values from 10 to 100 g/kg, preferably from 15 to 70 g/kg, and most preferably from 20 to 50 g/kg give good results. It has been observed that high levels of alkali metal carbonate in the coating layer lead to low moisture
20 affinity.
The coated sodium percarbonate particles according to the invention have usually a 90 % dissolution time of at least 0,5 min. It is in particular at least 0,9 min. Generally the 90 % dissolution time is at most 3 min. It is preferably at most 2,5 min. 90 % dissolution times from 0,5 to 3 min, preferably from 0,9 to
25 2,5 min give good results. The 90 % dissolution time is the time taken for
conductivity to achieve 90 % of its final value after addition of coated sodium percarbonate to water at 15°C and 2 g/1 concentration. The method used is adapted from ISO 3123-1976 for industrial perborates, the only differences being the stirrer height that is 1 mm from the beaker bottom and a 2 litre beaker
30 (internal height 183 mm, internal diameter 127 mm). High levels of alkali metal carbonate in the coating layer, preferably at least 70 % w/w, lead to rapid dissolution which is desirable. This is however not the case when highly alkaline silicate sources are used during coating e.g. where the SiC2/Na20 molar ratio is 1,0 or less. In this case the high alkalinity ensures rapid dissolution.
35 The coated sodium percarbonate particles according to the invention usually
have an attrition measured according to the ISO standard method 5937-1980 of

at least 0,05 %. The attrition is in particular at least 0,1 %. Attrition values of at most 5 % are usual. Values of at most 4 % are preferred. Attrition values from 0,05 to 5 %, preferably from 0,1 to 4 % are convenient.
The coated sodium percarbonate particles according to the invention usually 5 present a thermal stability, measured using microcalorimetry at 40°C, of at least 0,1 uW/g. The thermal stability is advantageously at least 0,2 uW/g. It is most preferably at least 0,3 uW/g. It is generally at most 12 uW/g. More particularly, it is at most 4 uW/g. Values of at most 3 uW/g give the best results. Thermal stabilities from 0,1 to 12 uW/g, preferably from 0,2 to 4 uW/g, most preferably
10 from 0,3 to 3 uW/g, give good results. The measurement of thermal stability consists of using the heat flow or heat leakage principle using a LKB 2277 Bio Activity Monitor. The heat flow between an ampule containing the coated sodium percarbonate and a temperature controlled water bath is measured and compared to a reference material with a known heat of reaction.
15 The coated sodium percarbonate particles according to the invention usually
present a mean particle size of at least 500 um. The mean particle size is advantageously at least-550 urn. It is generally at most 900 um. Preferably it is at most 850 um. Mean particle sizes from 500 to 900 um, preferably from 550 to 850 um give good results.
20 The coated sodium percarbonate particles according to the invention usually
present a specific surface area of at least 2 m^/kg. It is in particular at least 3 nfi/kg. The specific surface area is generally at most 6 m^/kg. It is preferably at most 5,3 m^/kg. Specific surface areas from 2 to 6 m^/kg, preferably from 3 to 5,3 m^/kg give particularly good results. The specific surface area for sodium
25 percarbonate is calculated from sieve analysis using a minimum of 5 sieves on the basis of the following formula : Specific surface area per unit mass wj = the weight fraction of particles in fraction i, dj = the particle density of sodium percarbonate (2140 kg/m3),
30 r[ = the mean radius of particles in fraction i.
The calculation assumes approximately spherical, non-porous particles.
The coated sodium percarbonate particles according to the invention usually contain a fraction of particles having a particle size superior to 1000 um of at most 30 % w/w. It is preferably at most 20 % w/w. Large fractions above
35 1000 um give rise to unwanted segregation of bleach from a detergent matrix on
6

handling and can have an undesirable appearance. The fraction of particles having a particle size superior to 1000 urn is usually at least 0,1 % w/w.
The sodium percarbonate core can be obtained for example by crystallisation from a bulk saturated solution of sodium percarbonate in a 5 crystalliser/classifier. Preferably, the sodium percarbonate core is obtained using a crystallisation process without salting-out agent. For instance, the crystallisation process described in the international patent application WO 97/01562 of SOLVAYINTEROX, the entire specification of which is incorporated herein by reference, is particularly useful for obtaining such sodium percarbonate core
10 particles. Other sodium percarbonate core particles that are particularly useful as core particles of the invention are those described in the international patent application WO 97/35951 of SOLVAY INTEROX the entire specification of which is incorporated herein by reference.
The coating layer can optionally contain other constituents.
15 The coated sodium percarbonate according to the invention can be prepared
by any known coating process adapted to this purpose. A particularly performant coating process consists in introducing into a mixer uncoated sodium percarbonate core particles and a coating solution obtained by mixing an alkali metal carbonate solution and an alkali metal silicate solution, operating the mixer
20 at a temperature from room temperature to 50 °C in order to distribute the coating solution on the surface of the core particles and to obtain wet coated particles, removing the wet coated particles from the mixer and drying them in a fluid bed dryer using a stream of hot air of a temperature from 50 to 90°C in order to obtain dry coated particles.
25 Consequently, the present invention also concerns this process.
In the process according to the invention it can be interesting to operate the mixer at a temperature higher than room temperature in order to maintain the stability of the coating solution and to avoid that the coating constituents crystallise too soon before they are brought into contact with the surface of the
30 sodium percarbonate core particles. This is especially the case when highly alkaline silicate solutions are used.
It is recommended not to use the mother liquor from the crystallisation process as coating solution in the process according to the invention.
In the process according to the invention chelating agents can be added to
35 the mixer. These agents can assure chelation of the transition~metal ion impurities^ which are responsible for the decomposition of the sodium percarbonate. Suitable
~7

chelating agents can be selected from polycarboxylate or polyphosphonate salts, as such or in acid form. Examples are polyaminocarboxylates such as EDTA or DTP A, polyaminomethylenephosphonates such as EDTMPA, CDTMPA and DTPMPA and hydroxyalkylenephosphonates such as hydroxyethylidenediphos-5 phonate. A convenient amount of chelating agent"is often selected from 0,5 to 20 g/kg sodium percarbonate.
The silicate solution used in the process according to the invention are usually characterised by their molar ratio SiO2/Na20. This ratio is advantageously at least 1. It is preferably at least 2. Good results have been 10 obtained with molar ratios of up to 4. The best results are obtained with ratios up to 3,3. Molar ratios from 1 to 4 and in particular from 2 to 3,3 are convenient. This molar ratio can be controlled by adding more or less alkaline source for instance NaOH.
The coating solutions used in the process according to the invention usually 15 contain at least 20 % w/w of total amount of coating agent (alkali metal silicate and alkali metal carbonate and optionally other agents). Most often it contains at least 25 % w/w of coating agent. This amount is generally at most 50 % w/w. Amounts of at most 35 % w/w are convenient. Amounts of around 30 % w/w are preferred. Amounts from 20 to 50 % w/w, in particular from 25 to 30 % w/w are 20 convenient.
The wet coated particles removed from the mixer advantageously contain 4 to 10 % w/w of moisture, advantageously 5 to 8 w/w of moisture. The dried coated particles preferably contain from 0,2 to 0,6 % w/w of moisture.
The coated sodium percarbonate particles according to the invention can 25 advantageously be used as active bleach constituent in detergent compositions.
The present invention therefore concerns also the use of the above described coated sodium percarbonate particles as active bleach constituent in detergent compositions.
The present invention also concerns detergent compositions containing the 30 above described coated sodium percarbonate particles as active bleach constituent and a builder, either zeolitic or non-zeolitic. The detergent compositions can also contain other constituents such as surfactants, anti-redeposition and soil suspension agents, bleach activators, optical brightening agents, soil release agents, suds controllers, enzymes, fabric softening agents, perfumes, colours and 35 processing aids. The incorporation of coated percarbonate into detergent
8

powders or granules with a bulk density of 0,4 to 1,0 g/cm^ and into detergent
tablets which are either zeolite or phosphate built is particularly advantageous.
Example
Sodium percarbonate was manufactured using the continuous aqueous 5 crystallisation process free from sodium chloride described in the international
patent application WO 97/35806. From this process material with the following
properties was generated :
Avox = 14,61 % w/w
Bulk density = 1,03 g/cm^ 10 Moisture pick-up = 6 g/kg
90 % dissolution time = 0,9 min
Attrition = 1,5%
Thermal stability =1,7 uW/g
Mean particle size = 779 urn.
15 1 kg of this product was placed in a ploughshare mixer operating at around
150 rpm. To the sodium percarbonate was added 103,1 g of a coating solution
containing:
200 g/kg anhydrous sodium carbonate,
206,2 g/kg sodium silicate solution which was a 48,5 w/w solids amorphous 20 sodium silicate solution with a SiO2/Na20 molar ratio of 2,0,
593,8 g/kg demineralised water.
The coating solution with 30 % w/w solids was added over a 2 min period,
with a further 3 min mixing. The wet product was then discharged into a fluid bed
dryer and fluid bed dried in air for 30 min with a bed temperature of 70°C. The 25 characteristics of the coated sodium percarbonate after treatment was as follows :
Coating : 3 % w/w total
Coating composition : 67 % sodium carbonate, 33 % sodium silicate
Avox = 14,01 % w/w
Bulk density = 1,05 g/cm3 3 0 Moisture pick-up = 41,3 g/kg
90 % dissolution time = 2,2 min
Attrition = 1,1 %
Thermal stability = 2,5 uW/g
Mean particle size = 772 um 3 5 Calculated specific surface area = 4,0 m2/kg
Fraction of material above 1000 um = 16 % w/w

In order to assess the effectiveness of the coated sodium percarbonate, two
detergent formulations were made by blending coated or uncoated sodium
percarbonate with a zeolite 4A built detergent to give the following
compositions: 5 Sodium linear alkyl benzene sulphonate = 8,3 % w/w
Ethoxylated tallow alcohol - 4,4 % w/w
Soap = 3,1 % w/w
Zeolite 4A = 27,6 % w/w
Sodium carbonate = 10,0 % w/w 10 Sodium acrylate/maleate copolymer = 4,4 % w/w
3,3 molar ratio SiO2/Na20 sodium silicate = 2,9 % w/w
Carboxymethylcellulose = 0,2 % w/w
Sodium EDTA = 0,.2% w/w
Optical brightening agent = 0,2 % w/w 15 Sodium sulphate = 6,3 % w/w
Moisture = 10,4 % w/w
Coated or uncoated sodium percarbonate = 15,0 % w/w
The 2 formulations generated were stored in sealed polyethylene coated
cardboard cartons at 32°C and 80 % RH for a period of 6 weeks. The Avox was 20 monitored using potassium permanganate titration during this stability trial. The
following results were generated :
Sodium percarbonate % Avox recovery = Avox after x weeks x 100
initial Avox
x = 2 x = 4 x=6
uncoated 70 51 43
coated • 78 65 53
The effectiveness of the coated percarbonate was also assessed by blending
coated or uncoated sodium percarbonate with a sodium tripolyphosphate built
detergent to give the following compositions : 25 Sodium linear alkyl benzene sulphonate = 6,8 % w/w
Ethoxylated tallow alcohol = 2,5 % w/w
Soap = 3,0 % w/w
Sodium tripolyphosphate = 37,2 % w/w
3,3 molar ratio SiO2/Na20 sodium silicate = 6,4 % w/w 30 Magnesium silicate = 1,6 % w/w
Carboxymethylcellulose = 1,0 % w/w

WE CLAIM:
1. Coated sodium percarbonate particles containing:
a) a sodium percarbonate core, and
b) a coating layer comprising at least 40 and at most 70 % w/w of an alkali metal carbonate, at least 30 and at most 60 % w/w of an alkali metal silicate,! less than 5 % w/w of the total coating of sulphate, borate and magnesium compound sjthe coating layer being obtained by using the alkali metal carbonate and silicate simultaneously in the form of a coating solution in order to obtain a uniform dispersion of the alkali metal carbonate and alkali metal silicate carbonate in the coating layer A and the fraction of coating layer being from 1 to 5 %
w/w of the coated sodium percarbonate.
"I
2. Coated sodium percarbonate particles as claimed in claim 1 presenting
an Avox of the kind as herein described from 12 to 15% w/w, a bulk
density from 0.9 to 1.2 g/cm3, and a moisture pick-up from 10 to 100
g/kg.
\3y Coated sodium percarbonate particles as claimed in claim 2 presenting the Avox from 13.9 to 14.4% w/w, a bulk density from 1.0 to 1.1 g/Cm3 and a moisture pick-up from 15 to 70 g/kg.
4. Coated sodium percarbonate particles as claimed in any one of claims 1 to 3 presenting a 90 % dissolution time from 0.5 to 3 min, preferably from 0.9 to 2.5 min, an attrition, measured according to the ISO standard method 5937-1980, from 0.05 to 5%, preferably from 0.1 to 4%, and a thermal stability, measured using microcalorimetry at 40°C, from 0.1 to 12 p.W/g, in particular from 0.2 to 4 W/g, preferably from 0.3 to 3 nW/g.
5. Coated sodium percarbonate particles as claimed in any one of claims 1 to 4 presenting a mean particle size from 500 to 900 |.im, preferably from 550 to 850 |u.m, a surface area from 2 to 6 m2/kg, preferably from 3 to
-12-

5.3 m2/kg, and containing a fraction of particles having a particle size superior to 1000 |j.m of at most 30 % w/w, preferably at most 20 % w/w.
6. Coated sodium percarbonate particles as claimed in any one of claims 1 to 5 wherein the sodium percarbonate core is obtained using a crystallisation process without salting-out agent.
7. Process for preparing the coated sodium percarbonate particles as claimed in any one of claims 1 to 6 in which uncoated sodium percarbonate core particles and a coating solution obtained by mixing an alkali metal carbonate solution and an alkali metal silicate solution are introduced into a mixer, the mixer is operated at a temperature from room temperature to 50°C in order to distribute the coating solution on the surface of the core particles and to obtain wet coated particles, the wet coated particles are removed from the mixer and dried in a fluid bed dryer using a stream of hot air of a temperature from 50 to 90°C in order to obtain dry coated particles.
8. Process as claimed in claim 7 wherein the alkali metal silicate solution is a sodium silicate solution presenting a molar ratio Si02/Na20 from 1 to 4, preferably from 2 to 3.3.
9. Detergent compositions containing the coated sodium percarbonate particles as claimed in any one of claims 1 to 6 as active bleach constituent and a zeolitic builder.
10. Detergent compositions containing the coated sodium percarbonate particles as claimed in any one of claims 1 to 6 as active bleach constituent and a non- zeolitic builder.
Dated this 30TH day of November, 2000
{NALINI KRISHNAMURT])
OF REMFRY & SAGAR
ATTORNEY FOR THE APPLICANTS
-13-

Documents:

in-pct-2000-686-mum-abstract(24-06-2004).doc

in-pct-2000-686-mum-abstract(24-06-2004).pdf

in-pct-2000-686-mum-claims(granted)-(24-06-2004).doc

in-pct-2000-686-mum-claims(granted)-(24-06-2004).pdf

in-pct-2000-686-mum-correspondence(24-06-2004).pdf

in-pct-2000-686-mum-correspondence(ipo)-(6-10-2006).pdf

in-pct-2000-686-mum-form 1(30-11-2000).pdf

in-pct-2000-686-mum-form 1a(24-06-2004).pdf

in-pct-2000-686-mum-form 2(granted)-(24-06-2004).doc

in-pct-2000-686-mum-form 2(granted)-(24-06-2004).pdf

in-pct-2000-686-mum-form 3(24-06-2004).pdf

in-pct-2000-686-mum-form 3(30-11-2000).pdf

in-pct-2000-686-mum-form 4(25-03-2004).pdf

in-pct-2000-686-mum-form 5(30-11-2000).pdf

in-pct-2000-686-mum-form-pct-ipea-409(30-11-2000).pdf

in-pct-2000-686-mum-form-pct-isa-210(30-11-2000).pdf

in-pct-2000-686-mum-petition under rule 137(24-06-2004).pdf

in-pct-2000-686-mum-petition under rule 138(24-06-2004).pdf

in-pct-2000-686-mum-power of authority(24-06-2004).pdf

in-pct-2000-686-mum-power of authority(30-11-2000).pdf

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Patent Number

210909

Indian Patent Application Number

IN/PCT/2000/00686/MUM

PG Journal Number

46/2007

Publication Date

16-Nov-2007

Grant Date

15-Oct-2007

Date of Filing

30-Nov-2000

Name of Patentee

SOLVAY [SOCIETE ANONYME]

Applicant Address

33, RUE DU PRINCE ALBERT, B-1050 BRUSSELS, BELGIUM

Inventors:

#	Inventor's Name	Inventor's Address
1	TOM CANDY	1,Pensam Gardens, Callands,Warrington, Cheshire
2	ALUN PRYCE JAMES	28, DOWHILLS ROAD, BLUNDELLSANDS, LIVERPOOL L23 8SW, UNITED KINGDOM
3	RICHARD ROSELER	Rue Pierre Marchand 31, B-1970 Wezembeek-Oppem
4	MANFRED MATHES	Markstrasse 9A, D-53557 Bad Honningen 251,
5	GRAHAM R. HORNE	33,Shanklin Close, Great Sankey, Warrington,Cheshire WA5 3JN

PCT International Classification Number

C01B15/10 ,C11D17/0

PCT International Application Number

PCT/EP99/03948

PCT International Filing date

1999-06-04

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA