Classifications

• • C—CHEMISTRY; METALLURGY
  • C11—ANIMAL OR VEGETABLE OILS, FATS, FATTY SUBSTANCES OR WAXES; FATTY ACIDS THEREFROM; DETERGENTS; CANDLES
  • C11D—DETERGENT COMPOSITIONS; USE OF SINGLE SUBSTANCES AS DETERGENTS; SOAP OR SOAP-MAKING; RESIN SOAPS; RECOVERY OF GLYCEROL
  • C11D3/00—Other compounding ingredients of detergent compositions covered in group C11D1/00
  • C11D3/39—Organic or inorganic per-compounds
  • C11D3/3942—Inorganic per-compounds
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B15/00—Peroxides; Peroxyhydrates; Peroxyacids or salts thereof; Superoxides; Ozonides
  • C01B15/055—Peroxyhydrates; Peroxyacids or salts thereof
  • C01B15/10—Peroxyhydrates; Peroxyacids or salts thereof containing carbon
  • C01B15/106—Stabilisation of the solid compounds, subsequent to the preparation or to the crystallisation, by additives or by coating
• • C—CHEMISTRY; METALLURGY
  • C11—ANIMAL OR VEGETABLE OILS, FATS, FATTY SUBSTANCES OR WAXES; FATTY ACIDS THEREFROM; DETERGENTS; CANDLES
  • C11D—DETERGENT COMPOSITIONS; USE OF SINGLE SUBSTANCES AS DETERGENTS; SOAP OR SOAP-MAKING; RESIN SOAPS; RECOVERY OF GLYCEROL
  • C11D17/00—Detergent materials or soaps characterised by their shape or physical properties
  • C11D17/0039—Coated compositions or coated components in the compositions, (micro)capsules

Definitions

• the present invention relates to an enhanced process for the preparation of coated sodium percarbonate (PCS) containing particles, the so obtained particles, as well as their use in detergent compositions.
• PCS coated sodium percarbonate
• sodium percarbonate or sodium carbonate peroxyhydrate, 2 NaCO 3 . 3 H 2 O 2
• detergent compositions contain among other components zeolites as builder material, enzymes, bleach activators and/or perfumes.
• Crystallisation processes comprising the crystallisation of sodium percarbonate from aqueous solution and the separation from this aqueous solution, e.g. with salting-out agents, such as sodium chloride, etc.
• Other processes make use of fluid bed reactors, wherein small seed particles are grown by spraying solutions of sodium carbonate and hydrogen peroxide in the appropriate stoechiometric ratio.
• fluid bed processes yield particles with a smooth surface and good attrition behaviour, however the need to introduce the reactants in solution and the subsequent energy intensive evaporation is economically detrimental.
• both processes have been combined, e.g. by coating in the fluid bed reactor seed particles obtained by crystallisation from solution.
• the interaction between sodium percarbonate and other formulation components in detergent compositions 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, e.g. by interposing a layer between the sodium percarbonate and its environment, called a coating layer.
• the object of the present invention is to provide an optimized and more energy efficient process for producing coated sodium percarbonate particles having an appropriate and easily adjustable sodium percarbonate content, being highly soluble and having good attrition resistance.
• the present invention proposes a process for the preparation of coated sodium percarbonate containing particles, comprising the following steps: (a) a manufacturing step of sodium percarbonate containing core particles, comprising the crystallisation of sodium percarbonate from aqueous solution and the separation from aqueous solution, (b) an at least partial drying step of the sodium percarbonate containing core particles, (c) a coating step comprising the application of a base coating on the so obtained core particles with one or more sodium percarbonate containing or generating solutions and/or suspensions, and optionally one or more additives, and (d) a drying step of the coated sodium percarbonate containing particles, wherein step (c) and/or (d), and optionally (b), are carried out in a fluid bed reactor and the global molar ratio between hydrogen peroxide and sodium carbonate in the sodium percarbonate containing or generating solutions and suspensions in step (c) is below 1,35 or above 1,65.
• the major advantage of such a process of the invention when operated with the given global molar ratio, is not only the enhanced cost effectiveness of the process itself due to reduced energy needs and reduced operating costs, but also the versatility of the resulting products allowing to reduce storage, handling and/or transportation costs.
• These savings e.g. the energy savings due to the process are to be understood as compared to a similar process using the same starting materials with the same solutions or suspensions (which, in practice, in order not to introduce unnecessary water are already used as concentrated as permitted by the operating conditions) and the same operating conditions, but where the global molar ratio between hydrogen peroxide and sodium carbonate in the sodium percarbonate containing or generating solutions and suspensions in step (c) is not according to the invention, i.e. between 1.35 and 1.65.
• the percarbonate particles obtainable with the above process are furthermore highly soluble and show adequate attrition behaviour, which are important requirements in the art.
• step (c) by using a global molar ratio between hydrogen peroxide and sodium carbonate in the sodium percarbonate containing or generating solutions and suspensions in step (c) of less than 1,35 not all of the sodium carbonate will be converted to sodium percarbonate.
• the resulting excess of sodium carbonate may be desirable, not only because this compound as such acts as a detergent builder, but also because it allows to adjust the content of sodium percarbonate in the PCS particles such that the particles are classified as non-oxidiser according to the standard test method 0.1 of the UN Manual of Tests and Criteria, 4th revised Edition, sub-section 34.4.1.
• Dangerous goods are chemical substances or articles containing chemical substances, which can pose threat to public safety or to the environment during transport through chemical, physical, or nuclear properties if not properly identified or packaged. If they are accidentally released undesirable outcomes such as fires and explosions can occur.
• the purpose of the various tests is to provide adequate protection against the risks to life and property inherent in the transportation of hazardous materials in commerce.
• percarbonate powders or particles are typically classified as oxidisers (Class 5 - Oxidising Substances / Division 5.1) according to the test method O.I of the UN Manual of Tests and Criteria, sub-section 34.4.1 (UN-0.1 test, Transport of dangerous goods, 4th revised edition) and must be labelled and handled accordingly.
• O.I the UN Manual of Tests and Criteria
• sub-section 34.4.1 UN-0.1 test, Transport of dangerous goods, 4th revised edition
• the sodium percarbonate particles of the invention preferably have a content of available oxygen (AvOx) below 12,0 % by weight.
• the content of available oxygen may be adjusted to any value below this limit, such as from 4,0 to 11,5 % by weight, preferably from 5,0 to 10,5 % by weight, as required or desired for the intended use by controlling the molar ratio between hydrogen peroxide and sodium carbonate in the sodium percarbonate containing or generating solutions and suspensions at values below 1,35, said molar ratio being preferably at least 0,01, more preferably at least 0,05.
• the content of available oxygen is measured by titration with potassium permanganate after dissolution in sulphuric acid (see ISO standard 1917-1982).
• the upper available oxygen content indicated above is not only sufficient for most needs in the art of detergent and bleaching formulation, but this available oxygen content is furthermore easily adjustable within these limits so as to provide particles which are ready for use by the detergent manufacturer in the formulation of its detergents, without the need for any further treatment, equipment or handling.
• the surplus of sodium carbonate is of particular use at a later stage for the detergent manufacturer, as the carbonate acts as a useful detergent builder.
• the sodium carbonate advantageously comprised in the above particles need not to be conditioned, handled and introduced separately in the final detergent composition, thereby reducing the number of discrete ingredient forms in the final detergent, without sacrificing any desirable property.
• sodium carbonate coatings comprising sodium percarbonate have an enhanced attrition behaviour, as compared to coatings solely composed of sodium carbonate.
• a stoechiometric excess of one reactant as compared to its co- reactants may be used to speed up a given reaction or to compensate for possible losses during reaction, especially where said reactant is susceptible of decomposition as in the case of hydrogen peroxide.
• nearly all the water introduced during the process must be eliminated at some point to obtain sodium percarbonate particles usable e.g. in detergent compositions.
• the bulk of the water from step (a) may be removed quite easily and without using much energy, e.g. in a centrifuge, the remaining water, as well as the water introduced in the subsequent coating step(s) with the different solutions and suspensions must be evaporated, e.g.
• an at least partial drying preferably yields particles having from 5 to 20 % by weight, preferably from 10 to 15 % by weight of free water content.
• One benefit of the invention stems from the fact that if a global molar ratio between hydrogen peroxide and sodium carbonate in the sodium percarbonate containing or generating solutions and suspensions in step (c) of more than 1,65 is used, sodium carbonate already contained in/on the at least partially dried core particles entering coating step (c) is converted to sodium percarbonate, which is not possible with processes of the prior art.
• the coated sodium percarbonate particles usually have a content of available oxygen (AvOx) of at least 12,0 % by weight, in particular at least 13,0 % by weight, contents of at least 13,5 % by weight being particularly satisfactory.
• the content of available oxygen is generally at most 15,0 % by weight, in particular at most 14,0 %, for instance at most 14,2 %, the content of available oxygen being measured by titration with potassium permanganate after dissolution in sulfuric acid (see ISO standard 1917-1982).
• PCS core particles obtained from crystallisation almost always contain salting-out agents, which are used to precipitate the sodium percarbonate from solution, usually about 3,5 to 5% by weight, an important part of these salting-out agents being contained in the remaining water (mother liquor) bound to the wet particles.
• these agents are not useful, neither in the PCS particles as such, nor in the detergent end product as they may even impair the detergent properties.
• they are disadvantageous for high PCS contents.
• the core particles from step (a) are washed before or during step (b) with a sodium carbonate containing solution or suspension.
• step (b) is effected in a centrifuge, it is particularly advantageous to wash the core particles with a sodium carbonate containing solution or suspension, because it not only allows to remove at least part of the enclosed salting-out agents, typically at least 20 % by weight, preferably at least 40 % by weight of the initially included salting-out agent(s), but it also introduces sodium carbonate instead, which may be used to further control the initial AvOx content as described in the first alternative above (and which, as already mentioned above, advantageously at a later stage act as a detergent builder) or which, in the second alternative of the invention, may subsequently be beneficially converted into its peroxyhydrate with the excess of hydrogen peroxide.
• the washing step has to be done carefully not to wash out the soluble sodium percarbonate. This is achieved by reducing its solubility in the washing solution or suspension, preferably by using relatively concentrated or even saturated sodium carbonate solutions, and/or by adjusting the temperature and/or time, and/or by any other appropriate method or combination known to the skilled person.
• the washed core particles preferably contain at most 3 % by weight, more preferably at most 2,5 % by weight of salting-out agents, with respect to the washed core particle.
• this washing of the core particles not only advantageously replaces at least some of the extraneous salting-out agents with sodium carbonate; but in fact, it does so without introducing further amounts of water into the washed and centrifuged particles compared to particles having only been centrifuged. No additional energy will be necessary to evaporate additional water, which would otherwise be introduced along with the sodium carbonate (i.e. dissolved or suspended in water).
• still further sodium carbonate in the form of solid sodium carbonate can be added to the partially dried sodium percarbonate core particles after a partial drying step (b) e.g. in a centrifuge.
• This solid carbonate is preferably included in the process before step (c) in the form of a fine powder or dust with a dso ⁇ 0,2 mm, which adheres on the still moist core particles.
• This may be achieved using a mixing system, which can be run batch or continuous, e.g. a ploughshear mixer from L ⁇ dige; a screw conveyor, which will usually run in continuous mode; a Flexomix-System from Hosokawa, etc.
• a mixing system which can be run batch or continuous, e.g. a ploughshear mixer from L ⁇ dige; a screw conveyor, which will usually run in continuous mode; a Flexomix-System from Hosokawa, etc.
• the systems mentioned are only examples and the skilled person will be aware of other systems, which are suitable to granulate small particles onto the wet granules.
• the dust can be directly introduced into the fluid bed granulator, preferably into the fluid bed during step (c) to avoid a direct loss with the upstreaming air, the inlet of the dust can be done near the bottom or near the spraying nozzles.
• a further advantage of such an embodiment is that fine powder or dust always occurring in such processes may be efficiently and conveniently recycled.
• the sodium carbonate dust may also contain sodium percarbonate.
• step (c) it is clear from the above that further sodium carbonate (possibly even containing sodium percarbonate) may be introduced as needed within step (c).
• the global molar ratio between hydrogen peroxide and sodium carbonate in the sodium percarbonate containing or generating solutions and suspensions in step (c) must be below 1,35 to allow for a protective yet detergent compatible coating and even for a non oxidizer classification or above 1,65 to allow for the peroxyhydration of the sodium carbonate already present in the particles entering the coating step (c).
• the use of an excess of hydrogen peroxide not only advantageously converts at least part of the carbonate already present in/on the particles into percarbonate, but that the energetic benefit outweighs by far possible losses of hydrogen peroxide.
• the coated sodium percarbonate particles of the present invention have a mean particle size of at least 300 ⁇ m, in particular at least 400 ⁇ m, and more particularly at least 500 ⁇ m.
• the mean particle size is at most 1600 ⁇ m, especially at most 1400 ⁇ m, values of at most 1000 ⁇ m being preferred, for instance at most 800 ⁇ m.
• the mean particle size of particles may be measured using a sieve set (containing at least 6 sieves of known sieve aperture) to obtain several fractions and weighing each fraction.
• the mean particle size in ⁇ m (MPS) is then calculated according to the formula
• the index i increases with increasing sieve aperture.
• k n+ i equals to 1800 ⁇ m and is the maximum size considered for the MPS calculation.
• the coating layer(s) present in the coated sodium percarbonate particles of the present invention represent(s) in general at least 0,1 % by weight of the core particles, in particular at least 0,5 % by weight and most preferably at least 1 % by weight.
• the coating layer(s) represent(s) in many cases at most 50 % by weight of the core particles, especially at most 35 % by weight, and most often at most 25 % by weight. Amounts of from 0,1 to 50 % by weight give good results.
• the coated sodium percarbonate particles of the invention have a good storage or in-detergent stability, and especially long-term storage stability, which can be expressed in two different ways. According to the first way, it is expressed as heat output at 40 0 C measured after storage of 1 g of the product during 12 weeks at 40 0 C in a closed ampoule of 3,5 ml.
• the measurement of heat output by microcalorimetry consists of using the heat flow or heat leakage principle using a LKB2277 Bio Activity Monitor.
• the heat flow between an ampoule containing the coated sodium percarbonate particles and a temperature controlled water bath is measured and compared to a reference material with a known heat of reaction.
• This long-term stability is generally less than 10 ⁇ W/g, in particular less than 8 ⁇ W/g, preferably less than 6 ⁇ W/g, and most preferably less than 4 ⁇ W/g.
• the long-term stability is expressed as the AvOx (or available oxygen content) recovery after storage of 1 g of the product for 8 weeks at 55 0 C in a closed ampoule of 3,5 ml.
• the AvOx recovery corresponds to the difference between the available oxygen content before and after the storage expressed as percentage of the initial available oxygen content.
• the available oxygen content is measured as explained below.
• This AvOx recovery is in many cases at least 60 %, especially at least 70 %, values of at least 75 % being very suitable, those of at least 80 % being preferred.
• the coated sodium percarbonate particles of the present invention usually have a 90 % dissolution time of at least 0,1 min, in particular at least 0,5 min. Generally, the 90 % dissolution time is at most 3 min, especially at most 2,5 min.
• the 90 % dissolution time is the time taken for conductivity to achieve 90 % of its final value after addition of the coated sodium percarbonate particles to water at 15 +/-1 0 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 of 10 mm from the beaker bottom and a 2 liter beaker (internal diameter 120 mm).
• the coated sodium percarbonate particles of the present invention usually have a bulk density of at least 0,8 g/cm 3 , in particular at least 0,9 g/cm 3 . It is generally at most 1,2 g/cm 3 , especially at most 1,1 g/cm 3 .
• the bulk density is measured by recording the mass of a sample in a stainless steel cylinder of internal height and diameter 86,1 mm, after running 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 cylinder.
• the coated sodium percarbonate particles of the invention usually have an attrition measured according to the ISO standard method 5937-1980 of at most 8 %, in particular at most 5 %, especially at most 3 %.
• the attrition is in most cases at least 0,05 %.
• the sodium percarbonate containing or generating solutions and/or suspensions are preferably chosen from (1) a solution or suspension of sodium carbonate optionally comprising sodium percarbonate and a solution of hydrogen peroxide or (2) a solution or suspension of sodium carbonate, a solution or suspension of sodium percarbonate and a solution of hydrogen peroxide, the molar ratio between hydrogen peroxide and sodium carbonate in the sodium percarbonate containing or generating solutions and suspensions being as described above.
• the above process further comprises one or more additional coating steps (c'), (c"), (c'"), ... between steps (c) and (d), one, more or all of these additional coating step(s) being optionally associated with (e.g. preceded by or concomitant to) an at least partial drying step, wherein each additional coating step comprises the coating of the particles from the previous step with one or more additives, and optionally one or more sodium percarbonate containing or generating solutions and/or suspensions, the composition of each coating being different from that of its adjacent coating(s).
• one or more, more preferably all of the additional coating step(s) and if applicable one or more, more preferably all of their optionally associated drying step(s) are carried out in fluid bed reactor(s).
• the additive(s) used in the additional coatings or optionally used for the base coating is/are preferably chosen from organic or inorganic stabilizers, builders, alkaline sources, fillers, flowability enhancers and/or glass corrosion protectors, such as alkali metal or alkaline-earth metal sulphates, bicarbonates, carbonates, citrates, phosphates, borates, silicates and/or chlorides, as well as their hydrates, polycarboxylate, polyphosphonate or polyhydroxyacrylate salts, as such or in acid form, for example polyaminocarboxylates like EDTA or DTPA, or polyaminomethylene-phosphonates like EDTMPA, CDTMPA or DTPMPA, or hydroalkylenephosphonates like hydroxyethylidenediphosphonate
• the invention pertains to coated sodium percarbonate particles obtained by a process as described above.
• such particles comprise a core of sodium percarbonate, obtained by the crystallisation of sodium percarbonate from aqueous solution and the separation from aqueous solution, and on said core a sodium percarbonate containing base coating optionally comprising one or more additive(s), wherein said base coating is obtained by a coating step comprising the application of a base coating on the so obtained core particles with one or more sodium percarbonate containing or generating solutions and/or suspensions, and optionally one or more additives, followed by a drying step of the coated sodium percarbonate containing particles, the global molar ratio between hydrogen peroxide and sodium carbonate in the sodium percarbonate containing or generating solutions and suspensions being below 1,35 or above 1,65.
• the sodium percarbonate core particles thereof preferably have a reduced salting-out agent content, typically reduced by at least 20 % by weight, preferably at least 40 % by weight of the initially included salting-out agent(s).
• the core particles therefore contain preferably at most 3 % by weight of the core particle, more preferably at most 2,5 % by weight of the washed core particle.
• These particles may further comprise on said base coating one or more additional coating(s) containing sodium percarbonate and/or one or more additive(s), the composition of each additional coating being different from that of its adjacent coating(s).
• a still further aspect of the invention pertains to the use of the coated sodium percarbonate particles as described above as bleaching agent in detergent compositions.
• a still further aspect of the invention is concerned with detergent compositions containing such coated sodium percarbonate particles.

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• 2008
  • 2008-04-29 WO PCT/EP2008/055253 patent/WO2008135461A1/en active Application Filing
  • 2008-04-29 EP EP08749854A patent/EP2144989A1/en not_active Withdrawn
  • 2008-04-29 CN CN2008800231916A patent/CN101688161B/zh not_active Expired - Fee Related

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