Composite composition comprising sodium percarbonate with improved solubility

This invention relates to a composite composition comprising granular sodium percarbonate with better stability in storage and fast solubility in water for the purpose of the sole use thereof or as a composition of a bleaching agent.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 This invention relates to a composite composition comprising granular
 sodium percarbonate with better stability in storage and fast solubility
 in water to be used by itself or as a composition of a bleaching agent.
 2. Description of the Prior Art
 The use of sodium percarbonate and sodium perborate in powder form have
 been used for many years as bleaching agents for clothes. When used as a
 beaching agent, sodium perborate requires an activator. Due to recent
 trends in environmental and energy conservation, there has been a demand
 for the use of sodium percarbonate which is readily soluble in cold water
 and does not require an activator. However, in order to be an affective
 bleaching agent, it is critical that sodium percarbonate not decompose
 during its delivery or storage, not lose any active oxygen, and quickly
 dissolve in water.
 A highly soluble form of sodium percarbonate is desirable in order to
 effectively wash cotton-based clothes. In a typical washing scenario,
 cotton based clothes, white clothes and dirty socks, are pre-soaked in
 water prior to washing. Sodium percarbonate is added to cold water
 together with a detergent and the clothes and left for a couple of hours
 prior to washing. If the sodium percarbonate particles can be readily
 dissolved in the wash water, damage or discoloration of the clothes may be
 prevented. Additionally, if the time needed to solubilize sodium
 percarbonate in unagitated water is shortened, the overall wash time may
 be shortened.
 In general, smaller particles are more readily dissolved in water,
 therefore selection of a smaller particled, micro-powder form of sodium
 percarbonate may shortened its solubilization time. However, in detergents
 containing zeolite, the zeolite significantly reduces the stability of
 sodium percarbonate. A sodium percarbonate micro-powder mixed with zeolite
 decomposes very quickly and makes it impossible to use sodium percarbonate
 as a component of a bleaching detergent. To lessen the decomposition
 affect, commercially available sodium percarbonate is in granular form
 instead of micro-powder. Accordingly, the granular sodium percarbonate's
 solubility in water is reduced.
 To solve these problems, many inventions related to the stabilization and
 composition of sodium percarbonate have been disclosed for the past 10
 years. Among these inventions, European patent No. 567,140 discloses a
 novel stabilization method in which the surface of sodium percarbonate
 particles are coated with boric acid or borate. However, this patent has
 disadvantages in that stability was not as good as expected, and the
 solubility rate in water was far slower than that of the conventional
 product.
 One conventional method to increase the solubility rate of sodium
 percarbonate in water is the thermal treatment of sodium percarbonate as
 disclosed in U.S. Pat. No. 3,953,350.
 Sodium percarbonate is decomposed at temperatures of more than 120.degree.
 C. to generate hydrogen peroxide, its primary decomposition product.
 Further, in parallel with the continuous decomposition, oxygen and water
 are generated as a final decomposition product, as disclosed in The
 Journal of Japan Industrial & Chemical Association (Vol. 47, No. 2, 1976,
 pp 84-90). These gaseous molecules remain trapped in the sodium
 percarbonate crystal lattice and are released when the sodium percarbonate
 is dissolved in water. This imparts a foaming action to the sodium
 percarbonate particles when they are dissolved in water. However, this
 method has proven to be uneconomical in that micro-powder is generated
 during the thermal treatment of sodium percarbonate, and the loss of
 active oxygen is inevitable.
 Japan Unexamined Patent Application No. Hei 9-227108 discloses a process to
 improve the stability and the solubility of sodium percarbonate when it is
 blended with detergents by coating the surface of sodium percarbonate
 particles. A description of the process is outlined below.
 A binder is added to wet sodium percarbonate prepared by the wet process
 method. The binder and sodium percarbonate mixture is then granulated. On
 average, particle sizes of up to 800 .mu.m are formed. Next, the mixture
 is dried and coated again using fluidized-bed technology. Coating
 materials include: amino acid derivatives, aliphatic, aromatic
 polycarboxylic acid and the salts thereof. The object of the invention
 recited in Japan Unexamined Patent Application No. Hei 9-227108) is to
 produce large particles of sodium percarbonate. However, in light of the
 adverse solubility effects associated with larger, granulated sodium
 percarbonate particles, it is questionable whether improved solubility is
 achieved in this process. Furthermore, this Japanese invention requires
 processing steps for the manufacture, fabrication and coating of the
 sodium percarbonate particles. The processing steps are very complicated
 resulting in enormous production costs.
 SUMMARY OF THE INVENTION
 The objective of the invention is to provide a stable, granular, sodium
 percarbonate composition and the process of manufacturing thereof, wherein
 the sodium percarbonate composition contains a compound designed to
 promote solubility of sodium percarbonate in water and a stabilizer in
 order to ensure that sodium percarbonate is not decomposed during
 transportation or storage, while said sodium percarbonate is readily
 dissolved in water.
 DETAILED DESCRIPTION OF THE INVENTION
 This invention provides a sodium percarbonate bleaching agent which has
 high solubility in cold water, high storage stability and relatively high
 concentrations of active oxygen. The invention has accomplished this by
 forming a composition of: sodium percarbonate, one or more stabilizing
 agents and one or more soubilizing agents and hydrogen peroxide.
 To achieve the embodiment herein, the composition of this invention
 includes sodium percarbonate generated by the reaction in which hydrogen
 peroxide solution is sprayed onto sodium carbonate anhydride, two
 well-known stabilizers, and one or more solubilizing promoters. The two
 well known stabilizers used are sodium silicate and magnesium sulfate. The
 solubilizing promoters may be selected from the following three groups, A,
 B, and C:
 A) an aliphatic or aromatic amino and its salts having one or more sulfonic
 acid groups, carboxyl groups or phosphonic groups;
 B) fatty acids having 10-12 carbons; polyols selected from sugars,
 polyhydroxy aldehydes, polyhydroxy ketones, and polyglycerines; esters
 formed from at least one of said fatty acids and at least one of said
 polyols, wherein a polyoxyethylene is added to said ester; and cyclic or
 open-chain forms of hemiacetals or acetals having more than four carbons.
 C) a polymer compound whose degree of polymerization is 50-10,000,
 expressed by the following chemical formula 1:
 ##STR1##
 wherein, m+n=100%, n is a whole number
 X represents --OH, --C.sub.6 H.sub.5, --C.sub.6 H.sub.5 SO.sub.3 M, or
 --COOH;
 Y and Z represent the same or different functional groups such as --H,
 --OPO(OH).sub.2, --OCOR, or --COOM;
 (R is an alkyl group having 1.about.4 of the number of carbon, and M is
 hydrogen or alkaline metal).
 Further, this invention is characterized in that one or more stabilizers or
 solubilizing promoters selected from the above three groups A, B and C,
 can be added either to the solution of hydrogen peroxide or the sodium
 carbonate anhydride for reaction in a mixing vessel.
 This invention is explained in more detail below.
 While sodium carbonate anhydride is being stirred in a mixing vessel
 together with commonly used stabilizers, hydrogen peroxide solution at a
 high concentration is sprayed into the mixing vessel. With the addition of
 a solution of hydrogen peroxide, the temperature of the reactants is
 increased. However, due to the wetting of the reactants by water, it is
 difficult to maintain or increase agitation. This lack of sufficient
 agitation, results in poor heat dissipation. To overcome this shortcoming,
 cool air is influxed into the mixing vessel so as to lower the temperature
 of the mixture and to adjust the amount of water. The sodium percarbonate
 particles generated under both proper stirring and cool air influx, are
 well massed without any decomposition. This situation results in properly
 sized granules. The granules are passed into the fluidized-layer dryer.
 Thus producing a granular sodium percarbonate. During the process, a small
 amount of micro-powder sodium percarbonate is generated. The micro-powder
 is recycled back to the mixing vessel for more enhanced yield. Actually,
 the process including reaction and drying according to this invention is
 applicable to the continuous industrial production.
 The stabilizers and solubilizing promoters of this invention, designed to
 better improve the stability and solubility of the sodium percarbonate
 produced in this process are described in detail below.
 Magnesium sulfate in a form of hydrates including pentahydrate or
 heptahydrate is a well-known stabilizer. Another well known stabilizer is
 sodium silicate including glass water and solid sodium silicate hydrate in
 various molar ratios (SiO.sub.2 :Na%O:H.sub.2 O).
 Some compounds belonging to A group are reagents which may form a complex
 with metal ions and include picolinic acid, taurine (2-Aminoethane
 sulfonic acid), sodium salt of N-(2-Hydroxyethyl)
 ethylenediamine-N,N,N-triacetic acid, NTA (nitrilotriacetic acid), EDTA
 (ethylene diamine tetra acetic acid), ATMPT [amino tri (methylene
 phosphonic acid)], and DTPMPA [Diethylene triamine penta (methylene
 phosphonic acid}.
 Further, some compounds belonging to B group include sugar, mannitol,
 sucrose and polyhydroxy aldehyde; or carbohydrates and glycerines with
 simple structures represented by polyhydroxy ketone, polyglycerine, and
 ester compounds containing both fatty acid having 10.about.20 carbons and
 above mentioned materials, such as glycerine fatty acid ester, sugar ester
 and other compounds where polyoxyethylene is added to ester compound
 consisting of polyol and fatty acid. Such ester compounds in a variety of
 forms have been manufactured for marketing based on the hydrocarbon
 contained in the fatty acid and the number of hydroxy groups (--OH)
 contained in the ester. The items commercialized by Sakamoto Co. include
 hexaglycerine monostearate and decaglycerine tristearate. Other
 commercialized items include; mono-, di-, and tri-sugar stearate by Ryoto
 Co.
 Some polymer compounds, expressed by the following chemical formula, which
 belong to the C group whose degree of polymerization is 50-10,000, are
 added to the reaction between sodium carbonate anhydride and hydrogen
 peroxide solution. These compounds contribute much to the adjusting of the
 size of sodium percarbonate particles, so generated, and the
 stablilization thereof. The appropriate polymer compounds include
 polystyrene sulfonic acid, polyacrylic acid, copolymer of both acrylic
 acid and maleic acid, polyvinylacetate and the derivatives thereof, and
 the salts where the functional groups of these compounds are substituted
 with alkaline metal.
 The amounts of the compounds contained in the above three groups (A, B and
 C) which are placed into a mixing vessel as solubilizing promoters for
 sodium percarbonate particles may vary according to the purpose of use.
 The proper amounts of such compounds to 100 wt % of sodium carbonate are
 as follows: the amount of compounds belonging to group A or B should be in
 the range of 0.015 wt %, while that of compounds belonging to C group
 should be in the range of 0.01-10 wt %.
 In order to prepare a granular sodium percarbonate of this invention having
 an excellent stability in storage and solubility in cold water, one or
 more compounds selected from the three groups (A, B and C) are added into
 the mixing reactor together with well-known stabilizers such as sodium
 silicate and magnesium sulfate to yield sodium percarbonate. These
 additives prepared in the form of solution or powder are continuously
 charged into a mixing vessel.
 This invention is explained in more detail based on the following examples
 but is not limited by the examples herein.

EXAMPLE 1
 A multi-purpose mixer (Mixer AR4010) produced by Erweka Co. of Germany was
 used as a mixing vessel designed to prepare sodium percarbonate. The
 mixing vessel equipped with a planetary stirring unit and rotary Teflon
 scraper is an useful instrument which can remove the reacting materials
 attached to the inside wall of the bottle and ensure the homogeneous
 mixing within a short period of time. The volume of the stainless mixing
 vessel is 5L (working capacity: 60%). The mixing vessel was cooled by
 dipping it into a thermostat consisting of ice and water.
 First, a mixture of sodium silicate pentahydrate (12 g) and sodium
 carbonate anhydride (800 g) was placed into the mixing vessel for
 sufficient stirring. Magnesium sulfate heptahydrate (5 g) and 60% hydrogen
 peroxide solution (500 g) in picolinic acid (5 g) were slowly sprayed onto
 the mixture of sodium carbonate and sodium silicate via a nozzle placed on
 the upper part of the mixing vessel. When the reaction was successfully
 completed by controlling the stirring and spraying rates, somewhat wet
 sodium percarbonate was moved to fluidized bed dryer (FBD) (rapid dryer TG
 100, Retsch Co. of Germany). The wet sodium percarbonate was dried at
 70.degree. C. for 10 minutes.
 The dried sodium percarbonate was sieved with mesh No. 20 and screened with
 the mesh No. 60. The particles, so selected, was stored in a humidity
 chamber (temperate: 32.degree. C. and relative humidity: 80% ) for two
 weeks in order to measure the active oxygen. Meanwhile, under the
 condition of no stirring, the time of solubilization of sodium peroxide to
 water at 20.degree. C. was measured by the method of conductivity.
 EXAMPLE 2
 Sodium percarbonate was prepared utilizing the same general procedure as
 described in example 1, however, 5 g of taurine(2-aminoethane sulfonic
 acid) was substituted in place of the picolinic acid used in example 1. A
 stability test was conducted and its results are found in the Table 1.
 EXAMPLE 3
 Sodium percarbonate was prepared utilizing the same general procedure as
 described in example 1, however, 5 g of Mg salt of
 N-(2-Hydroxyethyl)-imino diacetic acid was substituted in place of the
 picolinic acid used in example 1. A stability test was conducted and its
 results are found in the Table 1.
 EXAMPLE 4
 Sodium percarbonate was prepared utilizing the same general procedure as
 described in example 1, however, 6.5 g of Na salt of
 N-(2-Hydroxyethyl)ethylene diamine-N,N,N-triacetic acid was substituted in
 place of the picolinic acid used in example 1. A stability test was
 conducted and its results are found in the Table 1.
 Stability test
 A sodium percarbonate sample (2.0 g), as prepared in example 1, was placed
 in a 20 mL polyethylene bottle and sealed with an aluminium foil instead
 of a lid. Three needle holes were pierced into the aluminum foil for air
 flow. The polyethylene bottle containing sodium percarbonate was stored in
 a humidity chamber (temperate: 32.degree. C. and relative humidity: 80%)
 for two weeks in order to measure the active oxygen.
 The above described procedure was carried out for the remaining sodium
 percarbanate samples as prepared in examples 2-4. The results of the
 stability tests are summarized in Table 1.
 TABLE 1
 Example
 Stability
 Active oxygen on high
 No. Additives (%) humidity (%)
 1 Picolinic acid 5 g 13.70 92.0
 2 Taurine 5 g 13.64 93.5
 3 HIMDA, Mg salt 5 g 13.46 94.2
 4 HEDTA, Na salt 6.5 g 13.55 91.6
 EXAMPLE 5
 Sodium percarbonate was prepared utilizing the same general procedure as
 described in example 1, however, 6 g of lauryl acid sugar ester L-1695 was
 substituted in place of the picolinic acid used in example 1. A stability
 test was conducted and its results are found in the Table 2.
 EXAMPLE 6
 Sodium percarbonate was prepared utilizing the same general procedure as
 described in example 1, however, 6 g of lauryl acid sugar ester LWA-1570
 was substituted in place of the picolinic acid used in example 1. A
 stability test was conducted and its results are found in the Table 2.
 EXAMPLE 7
 Sodium percarbonate was prepared utilizing the same general procedure as
 described in example 1, however, 2 g of FA-090 (oleyl fatty acid ester
 having ethylene oxide of 9 mole) was substituted in place of the picolinic
 acid used in example 1. A stability test was conducted and its results are
 found in the Table 2.
 EXAMPLE 8
 Sodium percarbonate was prepared utilizing the same general procedure as
 described in example 1, however, 3.5 g of GLUCOPON 220 UP
 (alkylpolyglycoside) was substituted in place of the picolinic acid used
 in example 1. A stability test was conducted and its results are found in
 the Table 2.
 EXAMPLE 9
 Sodium percarbonate was prepared utilizing the same general procedure as
 described in example 1, however, 6 g of PS-35 (sodium polystyrene
 sulfonate) was substituted in place of the picolinic acid used in example
 1. A stability test was conducted and its results are found in the Table
 2.
 Solubility test
 1L of tap water was poured into a 1L beaker equipped with an conductivity
 measuring electrode. The temperature of the water was maintained at
 20.degree. C. using a thermostat. 5 g of sodium percarbonate, as prepared
 in example 5, was charged to the floor of the beaker to insure homogenous
 dispersion. The conductivity of the solution was measured until the sodium
 percarbonate was completely dissolved. Conductivity changes as a function
 of time were plotted using a graph recorder. The solubility time of the
 sodium percarbonate in stagnant water was determined at the instant when
 98.0% of the conductivity was lost when the sodium percarbonate was
 completely dissolved.
 The above described procedure was carried out for the remaining sodium
 percarbanate samples as prepared in examples 6-9. The results of the
 stability tests are summarized in Table 2.
 TABLE 2
 Time
 Active oxygen of solubility
 No. Additives (%) (min)
 5 L-1695 6 g 13.55 60
 6 LWA-1570 6 g 13.43 45
 7 FA-090 2 g 13.58 110
 8 GLUCOPON-220 UP 13.32 91
 3.5 g
 9 PS-35 6 g 13.64 50
 EXAMPLE 10
 In the same procedure as described in the example 1, sodium percarbonate
 was prepared for its stability and solubility tests with the addition of
 well known stabilizers sodium silicate pentahydrate (12 g) and magnesium
 sulfate heptahydrate (5 g), together with each of stabilizer or
 solubilizing promoter selected from the above groups A, B, C:

Category Amount
 Vinyl acetate derivative (DP 500) 8 g
 Taurine 3 g
 DTPMPA 2 g
 The results are summarized in the following table 3.
 EXAMPLE 11
 In the same procedure as described in the example 1, sodium percarbonate
 was prepared for its stability and solubility tests with the addition of
 well known stabilizers sodium silicate pentahydrate (12 g) and magnesium
 sulfate heptahydrate (5 g), together with each of stabilizer or
 solubilizing promoter selected from the above groups A, B, C:

Category Amount
 Vinyl acetate copolymer (DP 1700) 6 g
 Mannitol 4 g
 ATMPA 3 g
 The results are summarized in the following table 3.
 TABLE 3
 Time Stability
 Active oxygen of solubility on high
 No. Additives (%) (min) humidity (%)
 10 Vinyl acetate 13.58 40 94.8
 copolymer
 (DP 500) 8 g
 Taurine 3 g
 DTPMA 2 g
 11 Vinyl acetate 13.50 50 95.2
 derivative
 (DP 1700) 6 g
 Mannitol 4 g
 ATMPA 3 g
 COMATIVE EXAMPLE 1
 In the same procedure as described in the example 10, sodium percarbonate
 was prepared for its stability and solubility tests with the addition of
 well known stabilizers sodium silicate pentahydrate (12 g) and magnesium
 sulfate heptahydrate (5 g) in the absence of any additives. The results
 are summarized in the following table 4.
 COMATIVE EXAMPLE 2
 The stability and solubility test for sodium percarbonate (Degussa), which
 is now under market, were performed and its results are summarized in the
 following table 4.
 COMATIVE EXAMPLE 3
 The stability and solubility test for sodium percarbonate (Solvay-interox),
 which is now under market, were performed and its results are summarized
 in the following table 4.
 TABLE 4
 Time Stability
 Active oxygen of solubility on high
 No. Additives (%) (min) humidity (%)
 1 Blank 13.28 230 92.2
 2 Degussa 12.55 140 90.4
 3 Solvay-interox 13.45 160 93.5