CA1267347A - Soap encapsulated bleach particles - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

Hard spherical bleaching particles are disclosed whose composition is an intimately dispersed agglomerated core mixture of an active halogen oxidizing material, an inorganic diluent salt and a binder. The cores are coated with a mixture of from about 70-85% of a C16-C18 fatty acid soap and from about 15-30% of a C12-C14 fatty acid soap. A method for bleaching substrates and also a process for preparing the bleach particles are disclosed.

Description

~7~L~ 7 c ~4 (R) SOAP-E~CAPSU~ATED B~EACH P~RTICLE8 Th~ invention relate~ to coated halogen bleaah particle~ and a method ~or bleaching sub~trates through slow uniform release of a~tive halogenatin~ agent from the particle~.
Particle~ containing oxidants for bleaching ~ub~trateæ
have been wldely di~clo~ed in the literature. Much research ha~ focu~ed upon coating or encapsulating chlorinating agent~, e.g. dichloroisocyanurates granule~, to obtain delayed~ 810w relea~e of active oxidant.

When used for cleaning clothe~ in automatic washing machines, several problems ar~ noted wi~h encapsula~a oxidant~. Low bleaching ~trength i8 encountered becau3e of incomplete dis olution of the encap~ul.ates during the ~tandard wa~h cycle. Another proble~ i~ ~evere fabric colour damage from the localization of released bleach. Generally, bleaching products are placed into the automatic washing machine simul~aneously with the dry load. Bleach and fabric remain in close contact as the machine fill~ with water. Local high concentration3 of bleaahing activee th~reby come into contac~ with fabric surfaces. Under these condition~, very small spot~ re~embling pinholes appear on the fabric.

U.S. Patent 4,136,052 ~Mazzola) report~ to have solvad the pinhole problem cau~ed by locali3ed high concentrations of bleach. The patent provide~ a 3pecial coating which encapsulate~ the bleaching compound. An active chlorinating agent i8 ~urrou~d~d by a ~ir~t non-reactive coating combination o~ fatty acid and wax. A
second time controlled coating ia applied containing fatty ac~d with a material e~hibiting inver~e aqueou~
301ubility with re~pect to tempera~ure. The outer, ~ ,.

~econd coating i~ more re~istant to di~olution in hot than in cold water. By thi~ meanq, ~ufficient dqlay~d release is provi~ed in hot water to prevent pinholing.

U.S. Paten~ 3,908,045 (Alterman et al.) di~closes dichloroisocyanurate ~alt~ encapsulated wi~h a firRt coating of a saturated fatty acid ~urrounded by a second coating of ~oap. The latter coating is formed by trea~ment of portions of the inner fatty acid coating with a solution of an alkali met~l hydroxide.

The prior art compositions of soap-coated chlorine bleach provide adequate protection again~t pinhole type fabric damage only at low and medium wa~h temperatur23.
Unfortunately~ at hot wash temperature6, pinholing i~
still a problem. ~ ha~ been sugge~ted ~hat hot water pinholing results from non-uniorm coating, fabric damage b~ing caused by the inadequately encapsulated particle fraction~. Uniformly coated particle6 have, so far, been unobtainable. To solve.the problem, average coating weights have been increa~ed by a~ much as 50%
over the known art. Even these increaaed ~hickne~3es do not en~ure complete absence o~ pinholing at hot wash temperature~. Very thick coating6, which do control pinholing, are deficient because they hinder chlorine release at low temperatures and afford no bleaching.

Con~equently, it i8 an object of the pre~ent invention to provide bleach particles which eliminate pinholing yet have satisfactory active halogen release at all wash temperature~.

A further object of thi~ invention is to provide bleach particles that do not relea~e active halogen oxidant during the water fill cycle of an automatic w~ching machine but ~ubsequently completely relea~e active oxidant within the wash cycle~

C 6024 (R) 3~7 Another object of this invention is to provide a method for bleaching a variety o flexible or hard-~urfaced substrates.

Hard spherical bleaching particle~ are provided who~e composition is an intimately dispersed agglomerated mixture comprising:

(i) rom about 1 to 80% by weight of an oxidizing material having at least one reactive chlorine or bromine in its molecular structure;

(ii) from about 1 to 80% o~ an inorganic diluent salt;

(iii) from about 0,5 to 60% of a binder with melting point 85 to 120F~ and (iv) from about 5 to 50% of a coating covering a core mixtur0 of elements (i) through (iii) consisting essentially of a mixture of from about 70 to about 85%
alkali metal C16-C18 fatty acid soap and from about 15 to about 30% C12-C14 alkali metal fatty acid soap.

The present invention report~ improved coatings to encap~ulate core particles containing active halogen oxidi~ing agents. ~ncapsulation using a blend of fatty acid soaps of proper chain length has been found critical in guarding against pinhole damage whila still maximizing dis~olution rates to adequately relea~e the oxidi~ing agent. The effective soap blend comprises a mixture of coconut C12-C14 chain length fatty acids llow C16 C18 chain length fatty acids An increase in the coconut soap content of the coating increase~ the dissolution rate. Too much coconut soap, however, results in more pinhole damage. High tallow soap levels inhibit relea~e of oxidizing agent from the ~ 7 C 6024 (R) core when particles are di~per~ed in water; bleaching is thereby adver~ely affected. Conseqllen-tly, it is impor-tant to combina both types of ~oap to achieve a coating accentuating the advantages o~ each of the components.

The ^~oap coating may be applied to the core material at a level from about 5~ to about 50~ by weight of the particle; prefe~ably from about 20~ to 40~; rnore preferably from about 25% to 35%. A coating of approximately 30 wt.% soap provides sufficient insulation thickness to adequately overcome pinhole damage~ Substantially higher coating weights are wasteful. They only serve to inhibi~ early chlorine release during the wash cycle. Too little coating, of course, would relea~e oxidant too rapidly.

Among the coconut type soaps useful for this invention are the alkali metal, alkaline earth metal, a~monium, Cl-C12 alkyl ammonium and Cl-C6 mono-, di- or trialkanol ammonium salts of coconut fatty acid.
Coconut oil employed to prepare the soap may be obtained synthetically or from ropical nut oils including: palm kernel oil, babassu oil, ouricuri oil, tucum, oil, cohune nut oil, murumuru oil, jaboty ksrnel oil, khakan kernel oil, dika nut oil and ucuhuba butter.

Tallow soaps include the alkali metal, alkaline earth metal, ammonium, Cl-C12 alkyl ammonium and Cl-C6 mono-, di- or trialkanol ammonium ~alt~ of C16-Cl8 fatty acids. Rich ~ources of these fatty acids are beef tallow, lard, olive oil and shea nut oil.

The soap~ may contain ~ome unsaturation; however, substantial unsaturation is to be avoided. Active halogen could be reactive with the unsaturated fatty C 6024 (R) ~ ~;73417 acid soap. Sodium ~alts of the foregoing tallow and coconut fatty acid~ are particularly preerred.

The core material of the bleach particles i~ a granule comprising an oxidizing material, an inorganic diluent salt and a binder with melting point 85-120F.
Oxidizing material is, to a sub3tantial extent, hindered in release of active oxidizing agent by its dispersal in the diluent inorganic salt/binder matrix.
There are, however, ~till surfaces where the oxidant is exposed and readily available for release.

The coating of the present invention, when combined with the core granule, improves control over oxidant release. The soap blend coating of this invention effectively retards release of oxidant during the fill cycle of most automatic washing machines. Dissolution rate of the coating varies little wi~hin the temperature range of 70 to 135F, the range of common wash temperatures. Good chlorine release characteristics are observed at all common wash temperatures during the wash cycle interval. The soap blend is also unreactive toward the oxidant; the blend provides a shield against oxidant 1055 during storage of encap3ulated particles in detergent powder. With a protective coating of about 25-30~ by weight of the total particle, pinhole damage is prevented during the typical 4-minute washing machine fill cycle, even at high wa~h temperatures. Thereafter, particles dissolve rapidly during the agitation wash cycle. ~igh levels of bleaching agent are therefore available through most of the wash cycle.

The oxidizing material is one having at least a reactive chlorine or bromine atom in its molecular ~tructure. Among the suitable halogen donor bleaches are heterocyclic N-bromo and N~chloro imides such as ~7~7 c 6024 (R) -trichlorocyanuric, tribromocyanuric, dibromocyanuric and dichlorocyanuric acids, and salt~ thereof with water-solubilizing cations such as potas~ium and sodium.
Other N-bromo and N-chloro imides may also be u~ed such as N-brominated and N-chlorinated succinimide, malonimide, phthalimide and naphthalimide. Other compounds include the hydantoins, such as 1,3-dibromo-and 1,3-dichloro-5,5-dimethylhydantoin, N-monochloro-C,C-dimethylhydantoin methylene-bis(~-bromo-C,C-dimethylhydantoin); 1,3-dibromo- and 1,3-dichloro-5-isobutylhydantoin; 1,3-bromo- and 1,3-dichloro-5-methyl-5-ethylhydantoin; 1,3-dibromo- and 1,3-dichloro-5,5-isobutylhydantoin, 1,3-dibromo- and 1,3-dichloro-5-methyl-5-n-amylhydantoin, and the li~e. Further useful hypohalite-liberating agents comprise tribromomelamine and trichloromelamine.

Dry, particulate, water-qoluble anhydrous inorganic salts are likewise suitable for use herein, such as lithium, sodium or calci~ hypochlorite and hypobromite.

The hypohalite-liberating agent may, if desired, be provided in the form of a stable solid complex or hydrate. Examples include sodium p~toluene-sulpho-bromoamine trihydrate, sodium benzene-sulpho-chloramine dihydrate, calcium hypobromite tetrahydrate, calcium hypochlorite tetrahydrate, etc. Brominated ~nd chlorinated trisodium phosphate formed by the reaction of the corresponding sodium hypohalite solution with trisodium phosphate (and water if necessary~, likewise comprise efficacious materials.
Sodium dichloroisocyanurate is, however, the preferred bleaching source because of its great water solubility, ~734~ C 6024 (~) high chlorine content and dry storage stability when combined with -the other core components. Although it could be used, calcium hypochlorite i5 more reactive and tends to lose chlorine activity during storage.
Coarse grade sodium dichloroisocyanurate is used 80 that there i~ a high recovery of propar mesh ~ize particles. Thi9 material is commercially available under the trademark Clearon CDB, ~ product of the FMC
Corpora~ion.

Bleaching agents may be employed in admixtures comprising two or more distinct chlorine donors. An example of a commercial mixed æy t~m i8 one available from the Monsanto Chemical Company under the trademark designation "ACL-66" (ACL signifying "available chlorine" and the numerical de~Rignation "66" indicating the parts per pound of available chlorine). The material comprises a mixture of potassium dichloroisocyanurate (4 parts) and trichloroisocyanurate acid ~1 part).

By th0 term "reactive chlorine or bromine" is meant any o~idant capable of releasing halogen in the form of free elemental chlorine or bromine under conditions normally used for detergent bleaching purposes. It must also be understood that the hard spherical bleaching particles of this invention are not limite to their utility for washing fabric. They may also be used on dentures, floor~ and a variety of other hard or soft surfaces requiring cleaning with a controlled release oxidant.

In addition to the aforedescribed halogen-containing oxidan~s, there are numerou~ other Rimilar materials well known in the art. The li~t is by no means exhaustive. For instanee, suitable chlorine-releaqing agents are also disclosed in ~he ACS monogram entitled ~ 7347 ~ 6024 tR) "Chlorine - Its Manuacture, Properties and Uses" by Sconce, published by Reinhold in 1962.

When utilizing the particles of this invention in a detergent formulation, the desired chlorine level in a wash solution is about 10 to about 200 parts per million available chlorine. Preferably, the range i8 about 15 to 50 ppm for the most efficient utilization of chlorine-containing material as a brightener to be used with coloured clothes. The6e levels determine the amount of bleach particles which must be incorporated into a detergent formulation.

Anywhere from about 1 to 90% by weight of the total particle may be halogen-containin~ oxidizing material.
Preferably from about 30 to 70%, more preferably from about 40 to 60% of oxidizing material is present.

A n.lmber of different inorganic salts may be employed as the diluent. Examples include borates, nitrates, orthophosphates, tripolyphosphates, silicate~, sulphates, zeolites and clays. Sodium salts of the foregoing diluents are preferred. ~hese salts must be inert to oxidation. Sodium tripolyphosphate is an especially preferred diluent for the core granule. The inorganic salt diluent may be present in an amount from about 1 to 80~ by weight of the total granule.
Preferably, it should be present in an amoun-t from about 10 to 60~.
A third essential element is a binder with a melting point between 85 to 100F. Lauric acid is the binder of choice. It softens at common, low wash temperatures;
yet, it is still solid at room temperature. Higher chain fatty acids do not release bound chlorine at low wash temperatures. Fatty acids with lower melting points do not keep the particles firm during subsequent 1267~47 C 6024 (R) fluidization and encap-Rulating processing.
DichloroiRocyanurate is also stable when in contact with lauric acid during long period~ of ~torage.

S A particularly preferred binder i8 Emery 651, a product of the Emsry Chemical Company, a Division of ~ational Distillers Corporation. Emery 651 contains g6% lauric acid and 3% myristic acid; the melting point of this material is 106-lO9~F.
Suitable binders may also be found among organic homopolymers and copolymers. An example of a auitable homopolymer is polyvinylpyrrolidone.

A preferred embodiment of the core granules is one comprising a combination of dichloroisocyanurate, sodium tripolyphosphate and fat~y acid binder. When these components are procesYed at temperature~ above the fatty acid melting point, the surface tension of the resultant mixture i~ sufficient to render the granules spherical. No reaction occurs between the aforementioned components.

Core material is typically prepared by combining a bleaching agent Ruch as sodium dichloroisocyanurate with sodium tripolyphosphate and lauric acid in a rolling drum mixer. After brief mixing of components by rotation of the drum, heated air is blown through the compo~ition until a temperature is attained slightly above the melting point of the fatty acid.
Agglomeration of the tripolyphosphate and fatty acid binder around the dichloroisocyanurate granules is thereby accomplished. A combination of surface tension and action of the rotating drum cause6 the core components to draw together into ~pherical particles.
These are then cooled. The particles are ~creened to 18-25 U~S. Mesh with abou~ 70~ recovery. Oversized :~6~3'~'7 C 6024 ~R) agglomerates constitute the remaining 30%; these may be ground and recycled baclc to the mixer. Diluted core particles may be stored for subsequent encapsulation.
They are comple~ely stable under cool, dry storage conditions.

Encapsulation of the diluted core granules with the soap blend may be performed by a variety of methods. A
particularly praferred method is by the use of a spouted fluidiæed bed apparatu~.

The soap blend is dissolved in water to provide a solution of concentration from abo~t 5 to 40%;
preferably a soap solution of 15 to 304. Soap is then sprayed ~hrough an atomizing nozzle onto fluidized core granules held in the ~pout of the fluid bed. Water is continuously removed by the action of hot fluidized air passing through the bed. Bed temperatures are initially kept at 10-15F below the melting point of the fatty acid binder so that it will not melt and cause agglomeration of the particles. Drying rates are accordingly adjusted. Once the core granules have received an approximate 10~ coating, temperatures are increased to around 140F; thi3 permits an increased rate of application of coating resùlting from increased drying rates at the elevated temperatures. After the targeted soap blend thickne3s has been applied, the encap~ulates are fluidized for an additional 10-15 minutes to complete drying. A final water content of around 7~ may still be present in the particles.
Storage stability is una~fected by this level of water.

If desired, additional coatingq may be applied to envelope the prime coating of soap. For instance, the additional coating may be selected rom a cellulose material, organic homopolymPrs or copol~mer3, and mixtures thereof. Suitable cellulose materials may 1~7~47 C 6024 (R) include hydroxypropyl cellulose, hydroxypropylmethyl cellulose, hydroxybutyl cellulose and carbox~methyl cellulose. Examples of copolymer~ that may be employed include styrene-maleic monoalkyl e~ter~, ~tyrene-acrylic copolymers, maleic anhydride-acrylic and acrylic-methacrylic copolymer~. EIomopolymers may include poly~tyrene, polyacryla~e, polymethacrylate and polyvinylpyrrolidone.

Bleach particles of the present invention may be incorporated into a detergent composition containing surfactants, soaps, builder~, enzymes, filler materials and other minor functional laundering agents commonly found in such compo~itions.
1~
Surfactants present in the~e détergent composition~ may be found in an amount from about 2~ to 50~ by weight, preferably from 5 to 30% by weight. These surfactants may be anionic, nonionic, zwitterionic, amphoteric, cationic or mixtures thereof.

Among the anionic surfactants are water-soluble salts of alkylbenzene sulphonate~, alkyl ~ulphate~, alkyl e-ther ~ulphates, paraffin sulphonates, alpha-olefin sulphonates, alpha-sulphocarboxylates and their e~ters, alkyl glycerol ether sulphonates, fatty acid monoglyceride sulphates and sulphonate~, alkyl phenol polyethoxy ether sulphates~ 2-acyloxy-alkane-1-sulphonates and beta-alkoxy alkane sulphonates.
Nonionic ~urfactants are wa~er-soluble compounds produced by the condensation of ethylene oxide with a hydrophobic compound ~uch a~ an alkanol, alkylphenol, polypropoxy glycol or polypropoxy ethylene diamine.
Example~ of nonionic surfactant ar~ the conden~ation products o ethylene o~ide, propylene oxide and/or blatylene oxide with C8-C18 alkyl phenols, C8-C 6024 (R) ~7~7 C18 primary or secondary aliphatlc alcohols, C8-C18 fatty acid amides. The average moleR of ethylene oxide and/or propylene oxide present in the above nonionics varies from 1 to 30; mixtures of variou~
nonionics, including mixtures of nonionic~ with a lower and a higher degree of alkoxylation may al~o be used.

Cationic surfactants inalude the quaternary ammonium compounds having one or two hydrophobic groups with 8-20 carbon atoms, e.g. cetyl trimethylammonium halide ormethosulphate; dioctadecyl dimethylammonium halide or methosulphate: and the fatty alkyl amine~.

Zwitterionic surfactants are water-soluble derivatives of aliphatic quaternary ammonium, pho~phonium and sulphonium cationic compound~ in which the aliphatic moieties can be straight or branched, and wherein one of the aliphatic sub~tituents contains from about 8 to 18 carbon atoms and one contains an anionic water-solubili2ing group. ~xamples are alkyl dimethylpropane-sulphonate~ and alkyl dimethyl ammoniohydroxypropane-sulphonates wherein the alkyl group in both types contains from about 1 to 18 carbon atom~.
Conventional alkaline detergency builders, inoryanic or organic, may be found in these composi~ions at levels from about 2 to 80%, preferably from 10 to 50% by welght. Inorganic builders include water-soluble alkali metal phosphateq, polyphosphate~, borateæ, sllicates and carbonates. Organic builders include: (1) water-soluble amino polycarboxylate3, e.g. ~odium or pota~sium ethylene diamine tetraaaetates, nitrilotriacetates and N-(2-hydroxy) ethyl nitrilodiacetate~; (2) water-~oluble ~alts of phytic acid; (3) water-~oluble polyphoqphonate3 such as salts of ethane-l-hydroxy-l,l-diphosphonic acld; methylene ~67~34~ C 6024 (R) diphosphonic acid ~alts, ethylene dipho~phonic acid salts and ethane-1,1,2-triphosphonic acid ~alt~; (4) water-soluble ~alts of poLycarboxylate polymers and copolymers. Certain aluminosilicates such as synthetic zeolite~ can al~o be u~ed.

Adjunct materials commonly used in detergent compositions may be incorporated. These include 80il-suspending agents such as water-soluble salts of carboxymethyl cellulose, copolymers o maleic anhydride with vinyl ethers, and alkyl or hydroxyalkyl cellulo~e ethers. Other adjuncts include colorants, perfumes, lather boosters, anti-foam agents, optical brighteners, anti-oxidants and anti-corrosion inhibitors.
The following examples will more fully illustra~e the embodiments of the invention. All parts, percentages and proportions referred to herein and in the appended claims are by weight unless otherwise indicated.

73~ 7 C 6024 (R) Example 1 Preparation of Core Granules Core particles were found to be best prepared by a rolling drum process. This ~ethod provides strong, coherent core particles capable of withstanding a subsequent coating operation in a ~luid bed. The process involves pa~sing heated air (about 85 to lS0F) through a rolling drum ~illed with a mixture of granular halogen bleaching agent, inorganic salt diluent and a low-melting fatty acid (binder). A8 the fatty acid melts, it combines with the inorganic salt to intimately enca~e the chlorinat.ing agent. A nearly spherical core agglomerate i8 thereby created. Specific detail3 of ~he process are hereinater described.

A 4-foot long, 2-foot diameter rolling drum mixer was employed for the agglomeration. The drum was fitted with 6 inch spiral baf~les to promote better mixing. A
small motor rotated the drum at 32.5 rpm. Core particles were formea in batch runs of 50 lb raw material charge. Each charge con~isted of 35 lbs of coarse or fine-coarse Clearon CDB granules, 10 lbs of sodium tripolyphosphate and 5 lb~ of Emery 651 fatty acids. The~e materials were thoroughly blended by ro-tation of the drum for 10 minutes. Hot air was then blown through ~he drum to heat the core mixture.

As the temperature rose to the melting point of the fatty acids, the molten fatty acid mixture with sodium tripolyphosphate formed a coating around the Clearon CDB particles. After the reac~ant blend had reached 110F, it wa~ allowed to cool with continuing drum rotation. Upon cooling~ there resulted hard, coherent, nearly ~pherical particles. These particles were screened to obtain si~es in the range o~ 18-25 U.S.

~6'73'~ C 602~

Standard Me~h with 30-70~ of theoret.ical recovery.
Mea~ured chlorine content of the core particle~ ranged from 42 to 48~.

~

A 1.3 kilogram charge of core agglomerated granule~ was placed in an Aeromatic S~rea-l Fluid Bed. A mixture of tallow/coconut fatty acids of 80/20 ratio was dis~olved at 75C in water to provide a 22~ solution. Core granules were fluidized under agitation of an air flow at 55 cfm held at 30C. The bed was well fluidiYed under these conditions. Coating commenc~d by spraying the soap solution onto the fluidi~ed core granules from a spray nozzle located above the bed. Initially, the ~pray ra~e was held at 3 ml/min. This rate was maintained for about 68 minutes; approximately 3 wt.%
of coating was achieved at this point known a the "initial coating stage". Fluidization during thi~ and ~he ~ub~equent stage was di~icult due to the low attainable drying rates. Subsaquently, the ~pray rate could be increased to a maximum of 8 ml/min. at 30C.
During this stage, the coating thickne~s was sufficient to completely cover the core granule surface. With the contiguous coating, binder tackines~ was eliminated, thereby improving fluidi~ation. The bed was operated at the aforementioned spray rate for approximately 87 minute~ until a 10-12 wt.% soap coating had depo~ited;
this stage is termed the "low temperature coating stage".

The coating was now thick enough to overcome meltlng effects of fatty acid binder within the interior of the encapsulate. Temperatures and ~pra~ rates could now gradually be increased to 60~C and a maximum of 25 ml/min. Evaporation rates were greatly increa~ed owing to the higher ~ed temperature. Fluidization a~ this ~73~7 C ~024 (R) 1~

point wa~ excellent. Operation of the bed undar these condi~ions was continued for an additional 75 minutes.
The final coating reached 30 wt.~.

Further drying was performed at high temperature for an additional 10 minutes. Total encapsulation time was approximately 4 hours. Free-flowing encapsulated particles were obtained having approximately 25~ active chlorine. There was a 4~ active chlorine lo~ in the process due to the interaction of water solvent with the exposed core surface during the initial stage of encapsulation.

Example 2 Pinhole ~est Pinholing was evaluated by olacing the bleach particles on denim cloth swatches for four minutes in wash water held at specified temperatures. Denim cloth was used in the test because the dark navy dyes in the cloth are very susceptible to bleach damage. I'emperature used to simulate actual wash conditions were: hot - 135F;
warm - 100F; cold - 70F. A~ter the bleach particles had remained on the cloth underwater for 4 minutes in an unagitated state, they were agitated for 1 minute.
Thereafter, th~ denim was removed from tha wash water, rinsed and inspected for fabric dye damage. No effect on the colouring of the denim cloths was designated as excellent protection of the encapsulating coating.
Overall lightening of the cloth was designated as good.
Very light, localized BpotS wa~ designated as slight pinholing. Appearance of very light, readily distinguishable spots was designated as poor protection. When the cloth turned brown and was "burned" by the high chlorine concentration, this was designated as very poor protection.

~7~47 C 6024 (R) Chlorine Release Te~t . . . _ . _ The~e tests were conducted by placing a small sample of the bleached particles in a flask with wash water at the wa~h temperature. The solution was gently agitated for 4 minutes by slow turning of the flask in a rotating ~lask apparatus. The treatment was intended to simulate the fill cycle of a typical washing machine.

Subsequently, a ~ample of wash water was withdrawn and titrated with sodium thiosulphate solution. Chlorine content was established by this titration. The speed of flask rotation was then increasea to simulate the agitation cycle of a washing machine. At the 8, 12 and 16 minute marks, samples were withdrawn; the~e sample~
were titrated to establish ~hlorine content of the solution at each point of the wash cycle. The r~maining solution including any remaining parti¢les was then titrated to establiæh the extent of unreleasea chlorine. The test provides ~ reliable indica~ion of chlorine release expected in the non-agitated fill cycle and wash cycle of an automatic washing machine.

Performance of Encapsulated Bleach Granules The composition~ of various base soaps are outlined in Table I. Soap~ A through F are identifi d by the content and nature of their fatty acid conæti~uents.
Coating weight percentages and the identity of the soap(s) blend employed is listsd in Table II. Core composition~ are identified in the footnote wherein Na TPP refers to sodium tripolypho~phate and CDB refers to Clearon CDB, the chlorinating agent.

Performance of the encapsulates is ~et ~orth in Table III.

C 6024 (R) ~;7~

A blend of 6S~ coconut Soap F and 35% tallow Soap E
provided excellent chlorine release. However, the particles encapsulated therein dis~olved 80 rapidly that pinholing damage was considerable at 135F wash temperatures. Coating of Soap B, consisting o a 40/60 blend of coconut and tallow soaps, also provided good chlorine release. Pinhole damage, however, waa unacceptable. Coatings of Soap A appear to have the best dissolution prope~ties of the ~ncapsulates evaluated. Chlorine release into the wash was good and pinhole protection was maintained at all wash temperatures. Soap A consists of a 20/80 blend of coconut and tallow sodium soaps. Soap A of Sample 7 was prepared by the aforedescribed encapsulation method, except that water was replaced by acetone as the processing solvent. Acetone-processed encapsulates provided better performance than those processed with water. Compare the 8 minute chlorine relea~e value in Samples l and 7.
A further increase in tallow content reduced the performance of the encapsulate. A lO/90 blend of coconut and tallow sodi.um ~oaps (10% Soap F, 90~ Soap E) provided pinhole protection. Unfortunately, the encapsulated particles did not dissolve at low wash temperatures (70F3, resulting in poor chlorine release.

C 6024 (R) 1;~ 47 TABLE I

~ S ~ _ase Soa,~

- 5 Fatty Chain Soap Soap Soap Soap Soap Soap Acid Length* A B C D E F
(Tallow) (Coconut) Caprylic C8 1.2 2.7 - 6.8 - -Capric C101.1 2.5 _ 6.3 _ 1.0 10 Lauric C129 7 20.3 1.0 4g.3 - 96.0 Myristic C14 5.0 9.3 3.2 18.5 2.5 3.0 Palmitic C16 22.6 19.0 2S.6 9.0 50.0 Margaric C17 1.0 0.7 1.2 _ 1.5 Stearie Cl~16.5 12.6 19.6 2.2 45.5 15 Palmit- Clç.l2.6 1.9 3.2 - _ - _ oleic Oleic C18 1 34.7 27.0 41.0 6.1 - -LinoleicC18:2 2.1 1.5 2.5 ~ Chain lengths constituting les~ than 1~ are not shown.

C 6024 (R~
" ~2~7~3'~
~o TABLE II

Encapsulate Coatin ~ anules __ Sample Core Encapsulate Com~osition Coa~in~
1 I 100% Soap A

2 I 65% Soap F, 35~ Soap E

3 I 10% Soap F, 90% Soap E

4 I 25% Soap F, 75%, S II 100% Soap B
6 II 100~ Soap A
7 I 100% Soap A (acetone solven~
- . processed I - 70% CDB; 20~ Na TPP, 10% Emery 651 II - 10~ CDB; 80% Na~S04; 10% Emersol 132 ~ 7~347 C 6024 (R) TABLE III
Pin-Percentage o~ Chlorine Temper- holingRelea~ed ..
ature Per- Minute3

5 S~mple ~F) formance 4 81~ 16 1 70 Excellent 0 19.0 94.4 99.6 100 Excellent 0 90.1 100 100 135 Good 2.0 95.9 100 100 2 70 Good 0 84.6 98.7 100 100 Good 135 Very Poor 3 70 Excellent 0.9 0.9 0.9 4.2 100 Excellent - - - -135 Excell.ent 0.5 55.9 84.3 100 4 70 Good 0 4.5 29.5 52.4 100 Good - . - -135 Very Slight 7.2 96.3 g6.7 92.4 ~ 5 70 Poor - - - -100 Very Poor æ .0 31.6 59.0 84.1 135 Very Poor .- - - -

6 70 Good 100 Good 4.3 - 63.7 135 Very Slight 4.4 - 54.0

7 70 Excellent 0 45.1 89.9 96.6 100 Excellent - - - -135 ~ood 2.7 98.5 99.3 100.0 Unencapsulated 35 Core I
.

8 70 Very Poor 12.2 58.7 87.2 96.4 100 Very Poor 100 100 100100 135 Very Poor 100 100 100100 ~7;~47 C 6024 (R) The forego.ing description and example~ illustra~e selected embodiments of the present invention and in light thereof various modifications will be 3ugge~ted to one skilled in the art, all of which are within the spirit and purview o this invention.

Claims (20)

C 6024 (R) THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. Hard spherical bleaching particles whose composition is an intimately dispersed agglornerated mixture comprising:

(i) from about 1 to 80% by weight of an oxidizing material having at least one reactive chlorine or bromine in its molecular structure;

(ii) from about 1 to 80% of an inorganic diluent salt;

(iii) from about 0.5 to 60% of a binder with melting point 85° to 120°F; and (iv) from about 5 to 50% of a coating covering a core mixture of elements (i) through (iii) consisting essentially of a mixture of from about 70 to about 85%
alkali metal C16-C18 fatty acid soap and from about 15 to about 30% C12-C14 alkali metal fatty acid soap.

2. Particles according to claim 1, wherein the coating is present in an amount from about 25 to about 35% by weight of the total encapsulated particle.

3. Particles according to claim 1, wherein the oxidizing material is an alkali metal dichloroisocyanurate.

4. Particles according to claim 1, wherein the binder is lauric acid.

5. Particles according to claim 1, wherein the binder is selected from soap, polyvinylpyrrolidone and mixtures thereof.

6. Particles according to claim 1, wherein the oxidizing material is present in an amount from about to about 40%.

7. Particles according to claim 1, wherein sodium tripolyphosphate is the inorganic diluent salt.

8. Particles according to claim 1, wherein the binder is present in an amount from about 10 to about 30%.

9. A detergent composition comprising from about 0.5 to about 80% of hard spherical bleaching particles according to claim 1 and from about 2 to about 50% by weight of a surfactant selected from the group consisting of anionic, nonionic, zwitterionic, amphoteric, cationic surfactants and mixtures thereof.

10. A detergent composition according to claim 9, further comprising from about 2 to about 80% of an organic or inorganic builder salt.

11. A method for bleaching substrates, comprising applying the hard spherical bleaching particles of claim 1 suspended in an aqueous medium to said substrate.

12. A method according to claim 11, wherein the substrate is selected from the group consisting of fabrics, dentures, metals, ceramics and wood.

13. A process for preparing the bleaching particles of claim 1, comprising the steps of:

(i) mixing said oxidizing material, inorganic diluent salt and binder in a heated vessel to produce said core particles;

C 6024 (R) (ii) charging said core particles to a fluid bed dryer; and (iii) spraying a solution of said alkali metal C16-C18 fatty acid soap and C12-C14 alkali metal fatty acid soap coating mixture onto said core particles undergoing agitation in the fluid bed dryer, said solution comprising from about 0.5 to about 50% of said soap mixture and about 50% to about 99.5% of low-boiling organic solvent.

14. A process according to claim 13, wherein said solvent is selected from the group consisting of low-boiling alcohols, hydrocarbons, halocarbons, ethers, esters and mixtures thereof.

15. A process according to claim 14, wherein the solvent is selected from methanol, acetone and mixtures thereof.

16. A process according to claim 13, wherein the solvent has a boiling point of from about 40°F to about 250°F.

17. A process according to claim 16, wherein the solvent has a boiling point of from about 50°F to about 180°F

18. A process according to claim 13, wherein the fluid bed is maintained at a temperature of from about 50°F to about 300°F.

19. A process according to claim 13, wherein the temperature of the fluid bed dryer is maintained at from 10°F to about 200°F greater than the boiling point of said solvent.

C 6024 (R)

20. A process according to claim 13, wherein soap is present in the solution in an amount from about 5%
to about 40% by weight of the solution.