Classifications

• • 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
• • 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
  • 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
  • C01B15/12—Peroxyhydrates; Peroxyacids or salts thereof containing boron
  • C01B15/123—Stabilisation of the solid compounds, subsequent to the preparation or to the crystallisation, by additives or by coating

Definitions

• the present invention relates to a stable supersaturated aqueous solution of sodium perborate and its use for stabilizing sodium percarbonate particles.
• Particles of sodium percarbonate (2Na 2 C03. 3H 2 O 2 ) are used as active oxygen compounds in detergents, bleaches and detergents. Due to the insufficient stability of these particles during storage in hot and humid environments, as well as in the presence of various components of detergents and detergents, the sodium percarbonate particles must be stabilized.
• the common method used to stabilize sodium percarbonate particles is to coat them with an envelope of components with stabilizing action.
• application FR 2 419 252 discloses a process for the manufacture of sodium percarbonate particles stabilized by spraying in several stages, of these particles using a dilute aqueous solution of sodium perborate and a solution of sodium silicate. This method has the disadvantage of requiring several stages of spraying and intermediate drying. In addition, the sodium percarbonate particles thus stabilized have an unsatisfactory solubility and lead to an undesirable proportion of insoluble components.
• the stable supersaturated aqueous solution of sodium perborate according to the invention prepared from sodium metaborate, hydrogen peroxide and sodium silicate, comprises from 4 to 49% by weight of sodium perborate tetrahydrate, preferably from 9 to 49% by weight and sodium silicate in an amount such that the mass ratio of sodium metaborate used / sodium silicate is between 0.6 and 7.3 and preferably between 0.9 and 3.
• Such a solution can be obtained by mixing sodium metaborate, sodium silicate and an aqueous solution of hydrogen peroxide in a molar ratio sodium metaborate: hydrogen peroxide of approximately 1: 1.
• Such a solution is preferably prepared by bringing an aqueous solution of sodium metaborate containing sodium silicate into contact with an aqueous solution of hydrogen peroxide.
• the aqueous solutions advantageously used are those having a molar concentration of hydrogen peroxide close to that of sodium metaborate.
• the different components can be mixed in a reactor or a mixer (batch stirred reactor, static mixer).
• This supersaturated aqueous solution is stable over wide temperature limits, generally between 15 and 50 ° C and preferably between 20 and 40 ° C.
• solubility of a solid compound in a given solvent represents the maximum quantity (mass or molar) of this solid, which it is possible to dissolve in a certain volume of solvent at a given temperature.
• a solution is said to be supersaturated when its solute concentration is greater than the value of the concentration corresponding to the solubility at the same temperature. Such a solution will evolve by releasing excess solute in solid form until the concentration of solute reaches the value of solubility. There is then crystallization or precipitation.
• Supersaturation represents the difference to solubility and can be defined as the ratio between the concentration of the solute and the concentration to solubility.
• the supersaturated solution may have a delay in the release of excess solute in solid form. We then bet on latency or induction period.
• the applicant company has therefore discovered that the presence of sodium silicate, in the proportions indicated above, makes it possible to considerably increase the latency time of a supersaturated aqueous solution of sodium perborate and thus stabilize the supersaturated solution of sodium perborate. sodium and facilitate its implementation in different applications such as in particular in the process for manufacturing stabilized sodium percarbonate particles.
• Another object of the present invention is a process for the manufacture of stabilized sodium percarbonate particles, consisting of a sodium percarbonate core and a shell comprising sodium perborate tetrahydrate and sodium silicate. This process is characterized in that the sodium percarbonate particles are sprayed, moist directly after their manufacture or optionally followed by a drying step with stable supersaturated aqueous solutions of sodium perborate described above.
• the stable, supersaturated aqueous solutions of sodium perborate according to the invention which are particularly suitable for the process for the manufacture of stabilized sodium percarbonate particles, have a latency time greater than the time necessary for carrying out the coating.
• a latency of more than 15 minutes is preferred.
• a latency of more than 20 minutes is particularly preferred.
• the particles of sodium percarbonate having a moisture content of between 0 and 10% by weight, preferably between 0 and 7% by weight can be stabilized.
• the amount of water introduced per 100 g of dry sodium percarbonate particles is generally between 3 and 15 g and preferably between 3 and 12 g.
• the sodium percarbonate particles to be stabilized are prepared from sodium carbonate and an aqueous solution of hydrogen peroxide either by the dry route or by the wet route. The latter is advantageously chosen.
• the coating of the sodium percarbonate particles with supersaturated solutions of sodium perborate can be carried out in a mixer mechanical, centrifuge or filtration device.
• the amount of supersaturated sodium perborate solution to be used to stabilize the sodium percarbonate particles can vary within wide limits, it is generally between 25 and 600 g per 1 kg of dried sodium percarbonate particles and preferably included between 50 and 300 g.
• the sodium percarbonate particles thus stabilized are then dried in a fluidized bed drier at a temperature between 30 and 80 ° C and preferably between 50 and 70 ° C.
• the stability of the sodium percarbonate particles thus obtained is evaluated by determining the loss of active oxygen of a sample placed for one week in an oven at 30 ° C with 80% relative humidity.
• the dissolution rate of these particles thus stabilized is determined by the time necessary to obtain the dissolution of 90% of 2 g of sodium percarbonate particles introduced into a liter of water at 15 ° C.
• the aqueous solution of hydrogen peroxide contains 70% of hydrogen peroxide by weight.
• the sodium silicate used is of the 7 N 34 type sold by RHONE-POULENC and has a dry extract of 34%. (SiO 2 at 26.2% and Na 2 O at 7.8% by weight).
• An aqueous solution A is prepared from a 33% sodium metaborate solution, 7N34 sodium silicate and water.
• An aqueous solution B is also prepared having a molar concentration of hydrogen peroxide close to that of sodium metaborate in solution A.
• the aqueous solution A is introduced.
• the aqueous solution B is taken as time zero and the time necessary for the appearance of the first crystals of sodium perborate tetrahydrate (or the latency time) is visually measured.
• test sample is p grams and the volume of permanganate poured is n ml, the percentage of active oxygen is given by the following formula.
• the loss of active oxygen is defined as the difference between the initial active oxygen on 2 g and the final active oxygen on the final weight, expressed as a percentage of the initial content.
• Average particle diameter 800 ⁇ m
• the supersaturated aqueous sodium perborate solution prepared from 10.6 g of sodium metaborate, 7.8 g of the aqueous hydrogen peroxide solution is introduced over 16 minutes. 16.9 g of 7 N 34 sodium silicate and 67.5 g of demineralized water. The mixture is then left under stirring for two additional minutes.
• the sodium percarbonate particles thus coated, are then dried in a fluidized bed at approximately 55 ° C. At the end of the drying step, the amount of particles of sodium percarbonate recovered is 922 g and the particles have the following characteristics:
• Example 10 The procedure is as described in Example 10 except that a suspension of sodium perborate tetrahydrate containing 21.62 g of fine particles of sodium perborate with a diameter less than or equal to 50 ⁇ m, 1.32 g of metaborate is used. sodium, 16.9 g of sodium silicate 7 N 34, 1.14 g of the aqueous hydrogen peroxide solution and 61.94 g of demineralized water.
• the characteristics of the sodium percarbonate particles thus stabilized are as follows:
• Example 12 The procedure is as described in Example 10 except that the duration of introduction of the supersaturated sodium perborate solution is 43 minutes and then the mixture is stirred for an additional 3 minutes;
• Example 10 The procedure is as described in Example 10 except that the sodium percarbonate particles to be coated contain 5% moisture and that the supersaturated solution of sodium perborate comprises 43% by weight of sodium perborate and sodium silicate in quantity such that the mass ratio of sodium metaborate used / sodium silicate is identical to that of Example 10.
• the sodium percarbonate particles thus stabilized have characteristics identical to those obtained according to Example 10.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Inorganic Chemistry (AREA)
• Detergent Compositions (AREA)

Applications Claiming Priority (3)

Publications (1)

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Family Applications (1)

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• 1997
  • 1997-09-05 FR FR9711094A patent/FR2768140B1/fr not_active Expired - Fee Related
• 1998
  • 1998-08-05 WO PCT/FR1998/001741 patent/WO1999012848A1/fr not_active Application Discontinuation
  • 1998-08-05 KR KR10-2000-7002365A patent/KR100527255B1/ko not_active Expired - Fee Related
  • 1998-08-05 AU AU89881/98A patent/AU747168B2/en not_active Ceased
  • 1998-08-05 CN CNB988105403A patent/CN1134374C/zh not_active Expired - Fee Related
  • 1998-08-05 EP EP98941541A patent/EP1023239A1/fr not_active Withdrawn
  • 1998-08-05 JP JP2000510668A patent/JP2001515831A/ja active Pending

Non-Patent Citations (1)

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