Encapsulated halogen bleaches

Abstract: Active-halogen bleach encapsulated in a coating of a synthetic detergent either as a single coat or with an initial coating of a soluble inorganic builder or filler. The encap­ sulate being stable in highly alkaline environments such as detergent compositions.

Description: This invention relates to an encapsulated active-halogen bleach composition. The composition provides improved stability of the encapsulated oxidizing active-halogen in an alkaline environment such as in a detergent-bleach composition. Background of the invention The effectiveness of a detergent-bleach composition used in cleaning will vary depending on the temperature of the washing solution, the nature of the soil being removed, the nature and concentration of the active cleaner contained in the solution, hardness of the water and the like. One important consideration, in maintaining an effective concentration of bleach, is the stability of the bleach in the detergent-bleach composition. Typically, a halogen bleach in a detergent-bleach cleaning composition can react with other components in the cleaning composition such as sodium hydroxide and free moisture. This reaction during storage can result in a substantial loss of active-halogen and can result in a corresponding loss in the concentration of other cleaning components. Many encapsulating procedures known in the art suggests coating a particle of bleach to isolate it from other reactive components in a cleaner. However, many of these encapsulated beaches are not stable in highly alkaline environments. Further, encapsulating compounds such as tetrapotassium phosphate, hydratable inorganic salts and fatty acids having 12―22 carbon atoms must dissolve to release the active halogen. As a result, the encapsulating compounds generally remain in the washing solution and can interfere in either the washing or bleaching process. Further, these encapsulating compounds do not serve any other function other than encapsulating the active-halogen. An encapsulating compound which is also a cleaning compound, as in this invention, eliminates the introduction of unwanted compounds into the washing solution and reduces the cost of the detergent-bleach composition. Encapsulation of an active-halogen source with a single inorganic coating is known in the art. One example of such a composition is taught by Brubaker, U.S. Patent No. 4,279,764. Brubaker discloses a bleaching composition containing a chlorine bleaching agent coated with a silicate bound, hydrated, soluble salt containing an N―H chlorine accepting component. Brubaker discloses the prepared composition to be useful in preventing dye and fabric damage caused by bleach during machine washing of fabrics. Brennan, U.S. Patent 3,637,509 discloses an encapsulated mixture of an organic chlorinating agent and an alkali metal tripolyphosphate encapsulated by tetrapotassium phosphate. Brennan discloses that the composition provides an improved stability with respect to the available chlorine. Hudson, U.S. Patent No. 3,650,961, discloses a method of encapsulating a core component in a hydratable inorganic salt by means of a fluidized bed. Hudson notes that wherein the core component is, for example, a chlorocyanurate the composition is useful in detergent mixtures wherein the composition exhibits excellent chemical and physical stability. Alterman, U.S. Patent Nos. 3,983,254, and 3,908,045, disclose an encapsulated composition and a process for making the composition, wherein the composition comprises an encapsulated core and a coating of a fatty acid having 12―22 carbon atoms and, when the core is a chlorine releasing agent, with a second coating of a fixed alkali hydroxide. The Alterman patents note that the composition is effective in preventing pinholing by the bleach. Accordingly, a substantial need exists for an oxidizing halogen source that is stable in a highly alkaline environment, does not substantially degrade other cleaning components, and does not introduce unwanted and unnecessary components. Summary of the invention According to the present invention, there is provided an encapsulated active-halogen bleach composition that is compatible with a highly alkaline cleaning composition, that neither degrades the active components of the cleaning composition nor interferes with their action, which encapsulated active-halogen bleach composition comprises 30 wt-% to 80 wt-% of an active-halogen bleach core, 5 wt-% to 50 wt-% of an inorganic coating agent coated over the active-halogen bleach core, and 5 wt-% to 50 wt-% of an n-alkyl sulphate or sulphonate synthetic detergent coated over the inorganic coating agent. We have found that the isolation of the halogen source can be assured by applying two coatings to the halogen core, a first coat of an inorganic coating agent and a second coat of said synthetic detergent. The intermediate inorganic coating agent layer isolates the synthetic detergent from the halogen to insure that any minimal degradation is avoided and promotes adherence of the synthetic detergent coating to the active-halogen core. The detergent and the inorganic agent are used in the cleaning composition in which the encapsulated halogen source is combined. For the purposes of this application, a "halogen bleach", or "active-halogen" encompasses active-halogen containing oxidization and bleaching compositions which are capable of releasing one or more oxidizing halogen species (typically ―OCl―). For purposes of this application an "inorganic coating agent" as used herein, encompasses soluble inorganic compounds used as inert fillers in detergent compositions and soluble inorganic builders used in detergent compositions which contribute to the detergency of the composition, which do not substantially react with a halogen-bleach. Detailed description of the invention The encapsulated sources of halogen of this invention comprise a core of an active halogen compound and two coating layers. Halogen source The halogen releasing substances suitable as a core material include halogen components capable of liberating active halogen species such as a free elemental halogen or ―OX― wherein X is Cl or Br, under conditions normally used in detergent-bleaching cleaning processes. Preferably the halogen releasing compound releases chlorine or bromine species. The most preferred halogen releasing compound releases chlorine. Chlorine releasing compounds include potassium dichloroisocyanurate, sodium dichloroisocyanurate, chlorinated trisodium-phosphate, calcium hypochlorite, lithium hypochlorite, monochloramine, dichloroamine, [(monotrichloro)-tetra (monopotassium dichloro)]pentaisocyanurate, 1,3 - dichloro - 5,5 - dimethyl hydantoin, paratoluene, sulfondichloro - amide, trichloromelamine, N - chloromelamine, N - chlorosuccinimide, N,N' - dichloroazodicarbonamide, N - chloro - acetyl - urea, N,N' - dichlorobiuret, chlorinated dicyandiamide, trichlorocyanuric acid, and dichloroglycoluril. Dichloroisocyanurate dihydrate, the most preferred oxidizing chlorine source suitable as a core substance, is commercially available and may be obtained from Monsanto or FMC. The chemical structure of this compound is represented by the formula: NaCl₂C₃N₃O₃ · 2H₂O n-Alkyl sulphate or sulphonate synthethic detergent The synthetic detergent compound coating must remain sufficiently solid at temperatures likely to be encountered during storage of the product, for example, temperatures of about 15 to 50°C, and also remain stable at temperatures likely to be encountered during processing of the product into end use mixtures, for example, temperatures of about 15 to 95°C. A particularly suitable synthetic detergent for use as a coating in the present invention is preoxidized sodium octyl sulfonate. The sodium octyl sulfonate may contain 1,2 alkaline bisulfonate as a byproduct of manufacture which does not affect the performance of sodium octyl sulfonate as a coating in the invention. The organic compound coating is applied as a solution in a suitable solvent, water being preferred because of its compatibility and non-reactivity with chlorine releasing agents, non-flammability, and non-toxicity. Soluble inorganic coating agent Inorganic fillers suitable for coating agents include: alkalies such as sodium bicarbonate, sodium sequicarbonate, sodium borate, potassium bicarbonate, potassium sequicarbonate, potassium borate; phosphates such as diammonium phosphate, monocalcium phosphate monohydrate, tricalcium phosphate, calcium pyrophosphate, iron pyrophosphate, magnesium phosphate, monopotassium orthophosphate, potassium pyrophosphate, dry disodium orthophosphate, dihydrate trisodium orthophosphate, decahydrate tetrasodium pyrophosphate, sodium tripolyphosphate, sodium phosphate glass, neutral soluble salts such as sodium sulfate and sodium chloride; and silicates. Suitable builder compounds are tetrasodium and tetrapotassium pyrophosphate, pentasodium and pentapotassium tripolyphosphate, sodium or potassium silicates, hydrated or anhydrous borax, sodium or potassium sesquicarbonate, phytates, polyphosphonates such as sodium or potassium ethane - 1 - hydroxy - 1,1 - diphosphonate. When carrying out the process of the preparation of the compositions of the instant invention, the protective passivation coating of the invention is conveniently applied by means of the apparatus shown schematically in Figure 1. Referring to the drawings, a coating chamber or cylindrical tower 1 is shown, wherein the coating or encapsulation of the particles is accomplished. At the base of tower 1 is distributor plate 2. An unexpanded bed of the particles to be coated is contained in the tower 1. A downwardly projecting nozzle 3 constituting a spraying means is adjustably disposed within the tower 1, and adapted to be adjusted vertically so that the liquid droplets of coating material 6, discharged in a downwardly diverging three-dimensional spray pattern, would just cover the upper surface area of the bed. The coating solution is contained in vessel 5 and is fed to nozzle 3 by pump 7. The spraying of the coating solution 6 from nozzle 5 may be aided by pressurized air entering tower 1 at inlet 13. Fluidizing gas passes through duct 11 and is forced through the distributor plate 2 by blower 9 and is either cooled by cooling system 8, or heated by heat exchanger 10, if required, in order to maintain the fluidized gas within a desired temperature range. An exhaust blower 12 removes solvent vapors. A known weight of a multiplicity of particles to be coated is placed on the distributor plate 2. Air is caused to flow upwardly by the force created by blower 9 through duct 11, thereby expanding the thickness of the layer of particles, and maintaining the particles in continuous motion within the volume defined by the expanded bed, thus forming a fluidized bed 4. A solution of a solidifiable coating substance 6, contained in vessel 5, is sprayed by means of pump 7 through nozzle 3 on the fluidized bed 4 until all particles in the bed are completely coated. Particles coated by the above-described procedure are completely encapsulated with a continuous coating, and are free-flowing and nonagglomerated. It is important that each particle be fully covered to prevent the oxidizing halogen source from reacting with an alkaline environment. In order to apply an initial coating of an inorganic coating agent and a subsequent coating of a synthetic detergent, the double coating may be conducted in a single fluidized bed either by applying the first coat, emptying the solution tank 6, filling the solution tank 6 with the second coating solution and then applying the second coat; or with a dual coating solution inlet to the atomizer as shown in Figure 1 by coating solution 5A, coating solution tank 6A and the pipes leading from 6A to the pump 7, the fluidized particles in the bed first being coated with the inorganic coating agent contained in solution tank 5, this first coating being allowed to dry and then a second coating of the synthetic detergent contained in solution tank 5A being applied, both coatings being conducted in accordance with the previous discussion on the operation of the fluidized bed. Another method of applying a double coating in a fluidized bed is to coat the core particles with the inorganic coating agent in a first fluidized bed apparatus. The coated material then allowed to dry and placed in a second fluidized bed apparatus, wherein the encapsulated product produced in the first fluidized bed is coated with a second coating solution of a synthetic detergent. The fluidized bed operation conducted in accordance with the prior discussion of the operation of the fluidized bed. Before removal of the encapsulated oxidizing chlorine source from the fluidized bed the temperature in the bed can be increased so as to drive off any solvent remaining in the encapsulate. However, the temperature must remain below the melting temperature of the encapsulant and below the degradation temperature of the encapsulated core. In a most preferred embodiment, the encapsulate comprises 35 to 60 wt.% halogen bleach source core, 15 to 45 wt.% inorganic coating agent first coating, and 10 to 35 wt.% said synthetic detergent second coating. Preferably, the inorganic coating agent is a mixture of 10 to 40 wt.% sodium tripolyphosphate ad 60 to 90 wt.% sodium sulfate, the synthetic detergent is sodium octyl sulfonate and the core comprises particles having a particle size of 2 mm to 250 µm, preferably 2.38 mm to 125 µm. The detergent compositions with which the encapsulated bleaching agents of the invention find utility may have compositions represented by the following components and ranges of proportions hereof: Approximate percentage Anionic or Nonionic Detergent 1―90% Organic and/or Inorganic Builders (including alkaline builders) 0―95% Encapsulated bleaching agent 0.5―25% Optical brightener 0―0.3% Water 5―50% Filler 0―25% The encapsulated bleaching agents of the invention find particular utility in combination with solid cast highly alkaline detergent compositions. Other materials which may be present in such detergent compositions are those conventionally employed therein. Typical examples include the well-known soil suspending agents, corrosion inhibitors, dyes, perfumes, fillers, optical brighteners, enzymes, germicides, anti-tarnishing agents, and the like. The balance of the detergent composition may be water. The invention may be more fully understood by reference to the following example which includes a best mode. Example This example describes a dual coating process within the invention. Ten pounds of the encapsulated oxidizing chlorine source was made from 2.59 kg (5.71 lbs) of granular dichloroisocyanurate dihydrate with particle sizes of about 2 mm to 250 mm (about 60 U.S. Mesh). The particles were placed onto the distributor plate of the cylindrical coating tower 1 (Figure 1). The particles were fluidized and suspended by an upwardly moving air stream supplied by blower 10. The temperature of the bed maintained between 43 and 83°C throughout the coating process. The first coating solution was prepared by dissolving 1.23 Kg (2.71 lbs) of sodium sulfate and 0.41 Kg (.90 lbs) of sodium tripolyphosphate in 5.13 Kg (11.3 lbs) of soft water. The first coating solution was sprayed on the fluidized particles 3, through nozzle 5, appropriately adjusted as to height. The first coating solution was applied to the fluidized particles for a period of about 1 hour. The coated particles being of uniform size and being dry and free flowing. The second coating solution was prepared by dissolving 2.52 Kg (5.55 lbs) of 40% sodium octyl sulfonate in 2.52 Kg (5.55 lbs) of soft water. The second coating solution was sprayed on the fluidized particles in the same manner as the first coating was sprayed onto the core particles. The second coating solution was applied to the fluidized particles for a period of about 1 hour. The coated particles being of substantially uniform size and being dry and free flowing. After addition of the second coating the bed temperature is allowed to rise to about 82.2°C (180°F) to assure that no free moisture is left in the encapsulate. The encapsulates are then allowed to cool to less than 43.3°C (110°F) and discharged from the system. The specification and example are presented above to aid in the complete non-limiting understanding of the invention. Many variations and embodiments of the invention can be made without departing from the scope of the invention, as limited by the claims hereinafter appended.

Claims: An encapsulated active-halogen bleach composition that is compatible with highly alkaline cleaning compositions and that neither degrades the active components of the cleaning composition nor interferes with their action, which encapsulated active-halogen bleach composition comprises: (a) 30 wt-% to 80 wt-% of an active-halogen bleach core; (b) 5 wt-% to 50 wt-% of an soluble inorganic coating agent coated over the active-halogen bleach core; and (c) 5 wt-% to 50 wt-% of an n -alkyl sulphate or sulphonate synthetic detergent coated over the inorganic coating agent. A composition as claimed in Claim 1 wherein the soluble inorganic coating agent is a builder salt. A composition as claimed in Claim 1 wherein the soluble inorganic coating agent is an alkali metal phosphate compound, sodium sulfate, or a mixture thereof. A composition as claimed in Claim 1 wherein the core comprises 35 to 60 wt.% of a dichloroisocyanurate dihydrate based upon the composition; wherein the coating of soluble inorganic coating agent comprises 15 to 45 wt.% of a mixture of an alkali metal tripolyphosphate and sodium sulfate based upon the composition; and wherein the coating of synthetic detergent comprises 10 to 35 wt.% of an n-alkyl sulfonate based upon the composition. A composition as claimed in Claim 1, wherein the core comprises a particle of dichloroisocyanurate dihydrate having a particle size of 2 mm to 250 µm (10 to 60 U.S. mesh); wherein the coating of soluble inorganic coating agent comprises 15 to 45 wt.% of a mixture of 10 to 40 wt.% sodium tripolyphosphate and 60 to 90 wt.% sodium sulfate based upon the composition; and wherein the coating of synthetic detergent comprises 10 to 35 wt.% of a sodium octyl sulfonate based upon the composition. A composition as claimed in Claim 1 wherein the core comprises particles having a particle size of 2.38 mm to 125 µm (18 to 120 U.S. mesh).

Inventors: OLSON KEITH EDWARD, OLSON, KEITH EDWARD
Applicants: ECOLAB INC, ECOLAB INC.
Application year: 1985
Main classification: C11D17
IPC codes: C11D17, C11D3, C11D7, C11D11