Stable peracid bleaching composition

Abstract: A stabilized peracid bleaching composition contains per­ acid, preferably enzyme, and exotherm control agents (MgSO₄). By controlling the water level present, surprisingly improved stability of peracid, and enzyme, results. The pre­ ferred peracid is diperoxydodecanedioic acid. The enzyme of choice is protease. The dry product comprises separate granu­ lar, particulate and beaded components wherein the granular component is diperabic stabilised with an exotherm control agent, diluent and a binder that includes unneutralized poly­ meric acid, and is combined with enzymes. Other adjuncts in­ clude: a fragrance admixed with a water soluble starch to form fragrance beads; the particulate components such as agglom­ erated extender or bulking agent, a pH control agent, and pro­ tected fluorescent whitening agents. The water content of the granular diperacid is carefully controlled, as is the ratio of exo­ therm control agent to diperacid, to ensure both peracid and enzyme stability. An adhesive fragrance strip is adhered to the interior of the product container remote from the bleach prod­ uct.

Description: This invention relates to household fabric bleaching products, but more particularly to dry bleach products that are based upon stabilized organic diperacid compositions and especially products based upon the diperacid, diperoxydodecanedioic acid. Preferred forms of the invention contain enzymes, especially proteolytic enzymes. Bleaching compositions have been used in households for at least fifty to seventy-five years as aids in the bleaching and cleaning of fabrics. The liquid bleaches based upon the hypochlorite chemical species have been used most extensively. These hypochlorite bleaches are inexpensive, highly effective, easy to produce, and stable. The advent of modern synthetic dyes and their inclusion in fabrics has introduced a new dimension in bleaching requirements. Modern automatic laundering machines have also changed bleaching techniques and requirements. The increasing complexity of modern fabrics and laundering equipment has brought forth a need for other types of bleaching compositions. To satisfy this need and to broaden and extend the utility of bleaches for household use, other bleach systems have been introduced in recent years. Dry bleaching compositions based upon peracid chemical species are desirable new bleaching products. The peracid chemical compositions include one or more of the chemical functional grouping: The linkage provides a high oxidizing potential. This appears to be the basis for the bleaching ability of such compounds. One problem with such peracids is their tendency to undergo exothermal decomposition. Another is their inherently poor shelf stability. It has been determined that the tendency to decompose can be eliminated, or greatly reduced by mixing the organic peracids with diluents, or exotherm control agents. U.S. Patent 3,770,816 issued November 6, 1973 to Nielsen, and U.S. Patent 3,494,787 issued February 10, 1970 to Lund et al. discuss the use of hydrated alkali metal or alkaline earth metal salts as a mean to control the exothermal deterioration of peracids. U.S. Patent 4,100,095 issued July 11, 1978 to Hutchins et al. suggests the use of acids that liberate water upon heating, e.g., boric acid, as exotherm control agents. This patent however also indicates that the hydrated salts, are to be avoided as exotherm control agents. The patent notes that hydrated salts develop sufficient vapor pressure in the presence of diperacids to cause an increase in the loss of oxygen. The moisture level in dry peracid products can also affect their shelf-life. Since water facilitates release of active oxygen, careful control of its presence must be maintained in the dry bleach formulation, otherwise premature deterioration of the peracid takes place. Although the addition of exotherm control agents may effectively alleviate the decomposition problem, a new problem is introduced thereby. As the agents are added to the peracids, the amount of active oxygen released for bleaching is often reduced. Active oxygen is defined to mean the total equivalents of oxidizing moieties in the peracid compound. (See S.N. Lewis, "Oxidation", Vol. 1, Chap. 5, R. Augustine, Editor., Marcel Dekker, New York, 1969; pp. 213-258.) Actual active oxygen release is often less than the stoichiometric or theoretical yield calculated from the active oxygen content of the peracid. In any event, the addition of exotherm control agents reduces the level of the active oxygen yielded from unstabilized peracids and therefore reduces the efficiency of the peracid composition. This increases the per unit cost, or effectiveness of the stabilized peracid composition. Thus the solution of one problem raises another problem. In our copending application 86306442.4 (EP-A-0,214,789) there are described and claimed dry peracid based bleaching products, wherein the diperacid is preferably diperoxydodecanedioic acid. The dry product comprises separate granular, particulate and beaded components wherein the granular component is diperacid stabilized with an exotherm control agent, diluent and a binder that includes unneutralized polymeric acid. It is also desirable to include an enzyme in household cleaning products for stain removal purposes. Exemplary enzymes are selected from the group of enzymes which can hydrolyze stains and which have been categorized by the International Union of Biochemists as hydrolases. Grouped within the hydrolases are proteases, amylases, lipases and cellulases. However organic peracids, while useful in fabric bleaching, also appear to affect enzyme stability since enzymes are somewhat sensitive proteins which have a tendancy to denature or change their molecular structures in harsh environments. For reasons still unknown, enzymes may be denaturated in an environment where there is a concentration of peracid bleaching species. In U.S. Patent 4,501,681, issued to Grout et al, a dishwashing composition in which amylases and sodium perborate were combined, the patentees claimed that hypochlorite bleaches may deactivate amylases at the rather high pH's found in aqueous environments in which hypochlorite bleaches are used. In U.S. Patent 4,421,664, issued to Anderson, the claim was made that potential deactivation of enzymes from dry hypochlorite - yielding sources (potassium dichloroisocyanurate) could be controlled by using a reducing agent, thiosulfate, as a hypochlorite scavenger. Furthermore, efforts at including enzymes in a peracid - delivery system include U.S. Patents 3,840,466 and 3,637,339, both issued to Gray, which disclose combinations of enzymes, peracid activators and sodium perborate. However, stable combinations of sodium perborate and enzymes appear to be known. See, e.g., U.S. Patent 3,553,139, issued to McCarty. In fact, the McCarty reference and a number of others, e.g., U.S. Patent 3,676,352, issued to Grimm et al, suggest that enzymes could be conglutinated or encapsulated. While this encapsulation process might enhance enzyme stability, in fact, it would add a further processing step and make the manufacture more expensive and thus less cost-effective. A number of references suggest that peracids can be combined with enzymes as standard cleaning adjuncts, e.g., U.S. Patent 4,170,453, to Kitko, U.S. Patent 4,259,201, to Cockrell et al, U.S. Patent 4,011,169 to Diehl et. al. and U.S. Patent 4,128,495, to Mc. Crudden. In FR-A-2,229,766 (= GB-A-1,456,591) there is described a stable, phosphate-free, granular bleaching composition comprising (a) from 1% to 40% by weight of a normally solid water-soluble peroxyacid component selected from organic peroxy acids and salts thereof; (b) from 1.5% to 45% by weight of a stabilizing agent mixture consisting of: (i) magnesium sulfate; and (ii) an alkali metal sulfate selected from sodium sulfate, and potassium sulfate and mixtures thereof the weight ratio, on an anhydrous basis, of magnesium sulfate to alkali metal sulfate being from 60:1 and 6:1; and (c) from 5% to 45% by weight of water of hydration; the weight ratio of magnesium sulfate to peroxyacid compound being 1.5:1 or less. In EP-A-0,200,163 (published after the priority date claimed for the present application) there is disclosed a bleaching agent in the form of a uniformly composed granulate, containing a solid, aliphatic peroxycarboxylic acid and inorganic salt, which salt being capable of being hydrated, characterized by the fact, that the bleaching agent contains an organic polymer compound as a granulation aid, which is soluble in an alkaline-aqueous medium, by the fact, that all components are uniformly distributed in the individual grains of the granulate and by the fact, that the granulates exhibit a pH-value in the weakly acidic range in water alone. There is no disclosure in that specification of a composition which is within the claims of the present application. However, none of the foregoing references appears to have appreciated that an enzyme and peracid-containing product, in storage at relatively concentrated levels, can deleteriously affect the stability of the enzyme and therefore lessen the effective life and performance of such enzymes. There has heretofore been no appreciation of this phenomenon of rapid storage instability. The present invention seeks to ameliorate some or all of the above and other problems associated with diperacid based bleaching products. The present invention relates to organic diperacid based bleaching products as prepared for household use. The invention product is a stabilized peracid and enzyme bleaching composition wherein an active component is an organic diperacid, preferably the diperoxydodecanedioic acid. Additional components are present in the product to maximize the active oxygen available for bleaching purposes when placed into aqueous solution; to minimize the decomposition of the peracid while on shelf; and to reduce the objectionable odor of the diperacid. Preferably an enzyme, more preferably a protease, is present. According to one aspect of this invention an improved product is prepared by carefully controlling the moisture content of the peracid granule with respect to the amount of exotherm control. We have found this is advantageous for stability of the acid, moreover it serves to improve enzyme stability. More specifically, the bleaching product is based upon organic diperacids, and preferably upon diperoxydodecanedioic acid. An exotherm control agent, preferably a combination of Na₂SO₄ and MgSO₄ in the hydrated form, is admixed with the diperacid in critical amounts to optimize the active oxygen yield when the diperacid is used in aqueous environments, i.e., the laundering process, but yet affords exotherm protection. The water level present in the diperacid exotherm control component of the product is carefully adjusted so that minimum destabilization of the diperacid and enzyme is brought about by its presence, but at the same time, the exotherm control effects are maintained. The diperacid and its stabilizing agents may be prepared as a distinct granular component of the total composition. It is a principal object of the invention to provide an improved dry diperacid and enzyme bleaching product as according to claim 1 and a method as according to claim 14. It is another object of the invention to provide a diperacid bleach product having maximum active oxygen yield but retaining necessary exotherm control properties. It is another object of the invention to provide diperacid based bleaching product wherein the moisture content of the bleach and exotherm control agent is regulated to minimize deterioration of the enzyme and peracid during the product shelf-life but retaining effective exotherm control of the product and soil and stain removal potency. It is yet another object of this invention to provide a stabilized peracid and enzyme bleaching composition in which the enzyme need not be encapsulated, agglomerated or otherwise coated. Organic Peracids This invention relates to organic diperacids based bleaching products having the general structure: where R is a linear alkyl chain of from 4 to 20, and more preferably, 6 to 12, carbon atoms in the chain. These organic diperacids can be synthesized from a number of long chain diacids. U.S. Patent 4,337,213 issued June 29, 1982 to Marynowksi, et al, describes the production of peracids by reacting a selected acid with H₂O₂ in the presence of H₂SO₄. As noted above the organic diperacids have good oxidizing potential and are already known as useful bleaching agents. Diperoxydodecanedioic acid (hereinafter: DPDDA): is particularly preferred for use in the present bleaching product. It is relatively stable compared with other related diperacids and has desirable bleaching characteristics. Other peracids which are stabilized against exothermic decomposition by magnesium sulfate also appear suitable for use in the inventive compositions herein. Examples of potentially suitable peracids may include those enumerated in U.S. Patent 4,391,725, issued to Bossu. Amounts, by weight, of the peracid should preferably range from about 0.5 to about 50%, more preferably 2.0 to 40% and most preferably about 5.0 to 30% of the composition, when the peracid is included in a discrete granule. The peracid should deliver, in aqueous media, about 0.1 to 50 ppm A.O. (active oxygen), more preferably about 0.5 to 30 ppm A.O. An analysis for and a description of A.O., appears in S.N. Lewis, "Peracid and Peroxide Oxidations," in: Oxidation , pp. 213-258 (1969). Magnesium Sulfate Exotherm Control Agent Like the other peracids, however, DPDDA is subject to exothermic decomposition. Thus it is necessary to add as an exotherm control magnesium sulfate, to inhibit decomposition. The addition of exotherm control agents such as magnesium sulfate is known. However, in the present composition it has been discovered that if the amount of magnesium sulfate is carefully controlled, a maximum amount of active oxygen will be released from the DPDDA composition when placed into an aqueous environment. More specifically, the maximum yield of active oxygen is obtained if the magnesium sulfate in the peracid granule, is maintained in the range of less than 1:1, preferably from about 0.15:1 to 0.9:1; but most preferably from about 0.35:1 to 0.75:1 on a weight basis, MgSO₄ to DPDDA. Moreover, in the composition, magnesium sulfate should itself be present, by weight, in the range of preferably about 0.025% to 45%, more preferably about 0.1% to 30% and most preferably about 2.5 to 20%, when combined with DPDDA in a granular form. If the magnesium sulfate (the exotherm control agent) is increased above the critical levels noted above, the yield of active oxygen is reduced to unacceptable levels. If the exotherm control agent is reduced below the critical levels noted, the shelf-life stability of the DPDDA can be greatly impaired. It is also important that water be present in any admixture of the DPDDA and the exotherm control agent. In fact, the presence of water plays an important role in the exotherm control process as it acts to quench any decomposition of the diperacid. It is therefore necessary that the exotherm control agent have waters of hydration to serve as a source of water to stem the decomposition reactions. However, in this invention, the total amount of water present must also be carefully regulated to prevent enzyme and peracid instability. It is preferable to include the diperacid bleaching agent as a physically distinct and separate component in the product. Thus the diperacid is prepared as a granule also containing the magnesium sulfate. This granular component may thus include the diperacid, the exotherm control agent, the proper amount of water (should be present as waters of hydration), pH control agents, bulking agents, and binders. It has been surprisingly found that the water present in the DPDDA granule component should be adjusted to a level of not less than about 50% nor more than about 70% of the weight of MgSO₄. This level of water corresponds roughly to about MgSO₄ with four molecules of water. In the composition this most likely exists as a double salt of MgSO₄ and Na₂SO₄. At these levels, the diperacid remains stable, however, excess amounts of water interfere with the diperacid and enzyme stability. Enzymes A third, preferred, component to this invention is an enzyme selected from enzymes capable of hydrolyzing substrates, e.g., stains. Under the International Union of Biochemistry, accepted nomenclature for these types of enzymes is hydrolases. Hydrolases include, but are not limited to, proteases, amylases (carbohydrases), lipases (esterases) and cellulases. Proteases, especially so-called alkaline proteases, are preferred for use in this invention. Alkaline proteases are particularly useful in the cleaning applications of the invention since they attack protein substrates and digest them, e.g., problematic stains such as grass. Commercially available alkaline proteases are derived from various strains of the bacterium Bacillus subtilis . These proteases are also known as subtilisins. Nonlimiting examples thereof include the proteases available under the trademarks Esperase ® , Savinase ® and Alcalase ®, from Novo Industri A/S, of Bagsvaerd, Denmark, and those sold under the trademarks Maxatase ® and Maxacal ® from Gist-Brocades N.V. of Delft, Netherlands. See also, U.S. Patent 4,511,490, issued to Stanislowski et al. These commercially available proteases are supplied as prilled, powdered or comminuted enzymes. These enzymes can include a stabilizer, such as triethanolamine, clays or starch. The enzyme level, by weight, preferred for use in this invention is about 0.1% to 10%, more preferably about 0.25% to 3%, and most preferably about 0.4% to 2%. Other enzymes may be used in the compositions in addition to, or in place of, proteases. Thus, lipases, which digest fatty substrates, and amylases, which digest starch substrates, can be used in the compositions. These two types of enzymes are available commercially. Lipases are described in U.S. Patent 3,950,277, column 3, lines 15-55. Suitable amylases (and their sources) are Rapidase ® (Société Rapidase, France), Termamyl ® (Novo Industri A/S, Bagsvaerd, Denmark) and Milezyme ® (Miles Laboratories, Elkhurst, Indiana). Cellulases may also be desirable for incorporation and description of exemplary types of cellulases is found from the specifications of U.S. Patent 4,479,881, issued to Tai, U.S. Patent 4,443,355, isssued to Murata et al, U.S. Patent 4,435,307, issued to Barbesgaard et al and U.S. Patent 3,983,002, issued to Ohya et al. The problem with incorporating enzymes with peracid bleaches in a cleaning product became immediately apparent. There was a loss of stability. However, the source of the problem was not so evident. It is believed (although applicants do not intend to be bound by this theory) that the level of water present after manufacture of the peracid deleteriously affects the stability of the enzymes. Water remains in the peracid because the synthesis takes place in an aqueous environment and the exotherm control agent of choice herein, magnesium sulfate, will contain various amounts of waters of hydration in the final composition of the peracid granule. Thus, it appears that both residual water and bound water (waters of hydration) may harm enzyme stability if not carefully regulated. Applicants have surprisingly discovered that if the total water level present in their peracid-enzyme product is kept to within a critical level of between about 50% to 70% of the weight of the magnesium sulfate exotherm control, unexpectedly good stability results. More preferably, the level of water should be controlled to within about 50% to 65% and most preferably about 55% to 65% water with respect to the level of magnesium sulfate. If the water level exceeds the very narrow upper limit of the claimed critical range, instability will occur. On the other hand, if the water level is decreased to below the lower limit of the critical range, stability of the peracid would likely be deleteriously affected, since as the diperacid granule is produced, the water present in the magnesium sulfate appears to prevent or arrest decomposition of the peracid through mechanisms not completely understood. Thus, controlling the water level is critical from two perspectives: Too low a water level can give rise to a lack of exotherm protection of the peracid; too high a water level can impair both peracid and enzyme stability. These problems and now, their solution, had not been heretofore discussed or suggested in the art and this discovery represents a substantial advance thereover. Bleaching Composition Adjuncts When the peracid of this composition is in the form of discrete peracid containing granules, other components are necessary for inclusion in the diperacid granules. Sodium sulfate makes up the bulk of the diperacid granules. It cooperates with the MgSO₄ in retaining the water of hydration, and dilutes the diperacid, serving to isolate it from the other components in the peracid bleach granule. An organic dicarboxylic acid of the general formula: wherein R equals 1 to 9 carbon atoms, for instance adipic acid, is also desirable in the diperacid granules. It also serves to dilute the diperacid, and aids to adjust the pH of the wash water when the bleach product is used. The diperacid granule has its physical integrity maintained by the presence of binding agents. Particularly and especially desirable are polymeric acids, such as polyacrylic acid and methyl vinyl ether/maleic anhydride copolymers. Other polymeric acids which may provide this benefit include polyethylene/acrylic acid copolymers. Such materials serve as excellent binders for the granule components and make the granules resistant to dusting and splitting during transportation and handling. It has been found that DPDDA granules develop an off-odor, reminiscent of rancid butter, when compounded with the dicarboxylic acid, exotherm agent, neutralized polymeric acid binder, and bulking salts. However, unexpectedly if polymeric acid is added in the unneutralized (acid pH) form versus the neutralized form, the development of this unpleasant odor note is eliminated, or greatly reduced. These polymeric acids should therefore have a pH of substantially below 5, more preferably below 3, or most preferably about 2, when prepared as an aqueous solution of approximately 30 wt% polymeric acid. Fluorescent whitening agents (FWA's) are desirable components for inclusion in bleaching formulations. They counteract the yellowing of cotton and synthetic fibers. They function by adsorbing on fabrics during the washing and/or bleaching process, after which they absorb ultraviolet light, and then emit visible light, generally in the blue wavelength ranges. The resulting light emission produces a brightening and whitening effect, thus counteracting any yellowing or dulling of the bleached fabrics. Such FWA's are standard products and are available from several sources, e.g., Ciba Geigy Corp. of Basle, Switzerland under the tradename "Tinopal". Other similar FWA's are disclosed in U.S. Patent 3,393,153 issued to Zimmerer et al. Since the diperacid bleaching component of the product is an aggressive oxidizing material, it is important to isolate the FWA component from the diperacid as much as possible. As noted before, the diperacid is dispersed within granules wherein it comprises perhaps 20 wt.% thereof. Similarly it is advantageous to disperse the FWA's within particles separate from the diperacid granules. For this purpose. the FWA may be admixed with an alkaline material that is compatible therewith and which further serves to protect the FWA from the oxidizing action of the DPDDA content of the product. Thus the FWA may be admixed with an alkaline diluent such as Na₂CO₃, silicates. etc. The FWA is mixed with the alkaline diluent, a binding agent and, optionally a bulking agent, e.g., Na₂SO₄, and a colorant. The mixture is then compacted to form particles. These particles are then admixed into the bleach product. The FWA particles may comprise a small percentage of the total weight of the bleach product, perhaps 0.5 to 10 wt.% thereof. Furthermore, it is desirable to include the FWA in a particulate form wherein it is admixed with an alkaline diluent material. Thus, FWA is protected from the oxidizing action of the diperacid prior to actual use of the bleach product. A fragrance to impart a pleasant odor to the bleaching solution containing the diperacid product is also included. These fragrances are subject to oxidation by the diperacid. It is known to protect fragrances from oxidizing environments by encapsulating them in polymeric materials such as polyvinyl alcohol. Quite surprisingly, it has been determined that absorbing fragrance oils into starch or sugar also protects them from oxidation and affords their ready release when placed into an aqueous environment. Therefore, the fragrance, which is generally in the form of fragrance oils, is preferably absorbed into inert materials, such as starches, or sugars, or mixtures of starches and sugars. The absorbed fragrance and starch or sugar base is then formed into beads in which the fragrance is imprisoned. Thus, the fragrance is added to the bleach product in the form of beads. The fragrance beads are soluble in water. Therefore although the fragrance is protected from attack by the diperacid when the product is in the dry state, i.e., on the shelf, the fragrance is released into the bleach/wash water when the product is used. The fragrance beads are preferred in the product in amounts of perhaps 0.1-2.0 wt.%. Other buffering and/or bulking agents are also utilized in the bleaching product. Boric acid and/or sodium borate are preferred for inclusion to adjust the product's pH. The use of boric acid as a pH control agent is noted in British patent 1,456,591 published November 24, 1976. Boric acid may be included in the formulations as a pH adjustment agent in the range of about 1% to 60% by weight, more preferably about 2% to 50% and most preferably about 5% to 40%. Buffering agents include sodium carbonate, sodium bicarbonate, and other alkaline buffers. Builders include sodium and potassium silicate, sodium phosphate, sodium tripolyphosphate, sodium tetraphosphate, aluminosilicates (zeolites) and various organic builders such as sodium sulfosuccinate. Bulking agents, e.g., Na₂SO₄, or builders and extenders are also included. The most preferred such agent is sodium sulfate. Such buffer and builder/extender agents are included in the product in particulate form so that the entire composition forms a free-flowing dry product. The buffer may comprise in the neighborhood of 5 to 90 wt.% of the bleach product; while the builder/extender may comprise in the neighborhood of from 10 to about 90 wt.% of the bleach product. In order to maintain the product as a free flowing product and reduce dusting, it is advantageous to agglomerate the buffers/builders/extenders with a binder. Suitable binders for such purpose are polymeric acids , which were also referred to above as binders for the diperacid granules. In order to counteract the normally unpleasant odor of the DPDDA, a second source of fragrance is provided since the previously mentioned fragrance beads are generally insufficient to overcome the odor of the peracid composition when contained in a dispenser. Specifically, a small adherent strip (perhaps 19,35 cm² (3 square inches) in area) of fragranced material affixed to the inside of the bleach package at a location normally separated from the bleach formulation. This fragranced strip ideally is adhered to an inside upper flap of the bleach package. In such position, the fragranced strip is effectively removed from constant direct contact with the oxidizing component of the bleach composition and undesired oxidation of the admixed fragrance oil is avoided, or at least greatly reduced. Additionally, the use of a polymeric matrix material also affords protection of the entrapped fragrance from oxidation. Thus the fragranced strip comprises an amorphous, hydrophobic, self-adhering polymeric material into which fragrance has been intimately dispersed. The fragrance slowly volatilizes and permeates the air space within the bleach package to thereby counteract the undesirable odor emanating from the diperacid. The desired fragrance is dissolved in a matrix material, while the matrix material is at an elevated temperature, e.g., (65°-149°C (150-300°F). At such temperatures the matrix melts and the fragrance oil is readily admixed therein. Suitable matrix materials are ethylene/ethyl acrylate blends, polyethylene/polypropylene blends, polyamides, polyesters, and ethylene/vinyl acetate copolymers. Ethylene/vinyl acetate copolymers are preferred. Any such matrix material is selected for its ability to melt below a temperature above which a significant portion of the fragrance is volatilized. The material should also strongly adhere to the packaging material surface, e.g., laminated cartonboard, particle board, plastics, non-woven fabrics, etc., when solidified at room temperatures. The fragranced material is applied to the desired portion of the package interior as a hot melt. Upon cooling, the fragranced material strongly adheres to the package interior, where it slowly releases its fragrance to counteract the objectionable odor of the diperacid. A typical hot melt fragranced composition may contain from about 10 to 60 wt.% of the fragrance oil and about 10 to 75% vinyl acetate in the ethylene/vinyl acetate copolymer adhesive base. Such fragrance-adhesive mixture should have an equivalent hot melt index of from 1-50,000; and a hot melt ring and ball softening point of from 65-149°C (150-300°F). About 0.5-10 grams of the fragranced adhesive are applied in a strip to the package interior. By such means, the diperacid odors are effectively counteracted upon opening and when using the diperacid bleach product. The diperacid based bleaching product as described hereinabove provides an effective bleaching material when poured into water at which time active oxygen is released. The fragrance beads also dissolve at that time to release their fragrance and counteract any adverse odors released by the diperacid during the bleaching and/or washing cycle. Further preferred features of products embodying this invention are described and claimed in our European Patent Application 86306442.4 referred to above. DPDDA Granule Preparation The DPDDA granules are prepared by first producing a DPDDA wet filter cake, such as by the process of U.S. Pat. 4,337,213. Said filter cake is then mixed with the dicarboxylic acid, the exotherm control agents, bulking agents and the binder together to form a doughy mass. The mass is then extruded to form compacted particles. These particles are then partially crushed to form the granules and dried to reduce the moisture content down a level of about 50-70% of the weight of exotherm control agent (MgSO₄) present in the granules. A typical DPDDA granule is: 20 wt.% DPDDA - 10 wt.% adipic acid - 9 wt.% MgSO₄ - 6% H₂O - 54 wt.% Na₂SO₄ - 1 wt.% polyacrylic acid (unneutralized). TEST 1 To ascertain the effect of neutralized and unneutralized polymeric acid, two batches of DPDDA granules were made by the process discussed above. The granules comprised 20 wt.% DPDDA, 9 wt.% MgSO₄, 1 wt.% of a polymeric acid, 6 wt.% H₂O, 10 wt.% adipic acid, and 54 wt.% Na₂SO₄. In one batch, the polymeric acid solution (manufactured by the Alco Co. of Chattanooga, Tennessee and sold under the trademark Alcosperse® 157A) was neutralized to pH 5. In the companion batch, the polymer was unneutralized. This polymer had a pH of about 2. An expert olfactory judge found the rancid odor to be significantly higher in the granules containing the neutralized polymeric acid as contrasted to the granules containing the unneutralized polymeric acid. TEST 2 A test was run to determine the effect the water level in diperacid granules has upon storage stability. Two batches of DPDDA granules were made in accordance with the process disclosed above. Batch 1 Batch 2 DPDDA 20 wt.% 20 wt.% MgSO₄ 9 9 Binding agent 1 1 Adipic acid 10 10 H₂O 6.2 10.8 Na₂SO₄ remainder remainder The respective granules were then admixed to give compositions as follows: DPDDA Granules 37.62 wt.% pH control particles (Boric Acid) 16.9 FWA Particles 4.2 Fragrance Beads 0.66 Bulking Agent (Na₂SO₄) 40.62 The respective compositions were stored at 38°C (100°F) for periods of 2 and 4 weeks at which time the loss of DPDDA was determined. The results were as follows: Percent DPDDA Lost Batch 1 Batch 2 2 weeks storage 15.6 30.2 4 weeks storage 23.3 65.4 The results show that adjusting the water to a level of 50-70% by weight of the MgSO₄ substantially increased the stability of the DPDDA. TEST 3 A further test was conducted to ascertain the effect the exotherm control agent has upon active oxygen released during the wash/bleach process. Three batches of DPDDA were prepared as granules in accordance with the process disclosed above. Their compositions were: Batch 1 Batch 2 Batch 3 DPDDA 20 wt.% 20 wt.% 20 wt.% MgSO₄ 9 15 22 Binding agent 1 1 1 Adipic acid 10 10 10 Water 50 - 70% by weight of MgSO₄ Na₂SO₄ remainder remainder remainder Equal portions of each respective batch was then placed into wash water under identical washing conditions and the total amount of active oxygen released was measured. The results were as follows: Batch 1 Batch 2 Batch 3 % of active oxygen released 96.8 100 81. 3 The results illustrate that when the ratio of MgSO₄ to DPDDA increases to a level greater than about 1:1, then the release of active oxygen substantially decreases. The examples which follow hereto are illustrative of our improved enzyme and peracid containing formulations: DPDDA Granules 9.4 wt.% Boric Acid 11.5 FWA Particles 4.0 Fragrance 0.5 Enzyme 0.75 Bulklng Agent 73.85 (Na₂SO₄) 100.0% A test was conducted to determine whether a formulation which contained the critical amount of water claimed in the application would show better results than formulations outside this invention. As a result, the formulation of Example 1 was modified in two test runs to yield two samples which contained amounts of water higher than the critical range and then subjected to elevated temperatures (37,8°C (100°F)) for two weeks to simulate advanced aging (to ascertain enzyme stability and thus simulate product shelf-life). Test 4 Formulation of Example 1 with: A B C (invention) Actual H₂O levels: 13% 8% 5% % H₂O: 144.4% 88.9% 55.6% Two week stability: 16.0% 11.0% 65.3% The results above demonstrate that if the critical level of water is exceeded, enzyme stability drops drastically. This result was highly surprising since one, upon reading the prior art, would be led to assume that enzymes could be added to peracid formulations without any consideration of their stability therein. Further, in another comparison test, the stability of an enzyme-containing formulation which is substantially similar to that disclosed in U.S. Patent 4,100,095, issued to Hutchins et al, was compared against the inventive composition in a closed container. In the Hutchins et al reference, the patentee maintained that hydrated salts used as exotherm control agents suffered from several defects. Consequently, the reference maintained that certain water-releasing materials, specifically, selected acids, such as boric acid, would improve the peracid stability. Hutchins et al however, did not disclose, teach or suggest the use of enzymes in a peracid composition. Surprisingly, the applicants discovered that their inventive compositions had superior enzyme stability in a closed environment over a Hutchins type composition containing virtually the same amounts of peracid and enzyme. (Note: in the formulations below, enzymes were added to a Hutchins type formulation, since Hutchins et al did not suggest, disclose or teach the addition of enzymes). The formulations were compared as follows: Inventive Formulation Hutchins Formulation Component Wt.% Component Wt.% DPDDA granules 30.1 DPDDA 7.4 Boric Acid 13.4 DDA 1.8 FWA Particle 4.0 Boric Acid 13.4 Fragrance 0.5 Na₂SO₄ 67.6 Enzyme 1.0 FWA 0.4 Enzyme 1.0 Na₂SO₄ 51.0 Misc. 8.4 100.0% 100.0% The results of a four week stability study conducted at 21,1°C and 37,8°C (70°F and 100°F) were: Test 5 Formula Temp. 21,1°C (70°F) 37,8°C (100°F) 1. Inventive 79.0 47.0 2. Hutchins 60.0 12.0 As the above test results show, the inventive compositions have better long term and elevated temperature stability than a direct example of the prior art. Applicants are uncertain why their formulations are so much more stable, but, without being bound by theory, applicants speculate that the absence of magnesium sulfate as a control may lessen the stability of the peracid enzyme compositions, for reasons presently unknown. It is further speculated that when DPDDA is combined with an acidic pH control agent, such as boric acid, without the peracid granule of the invention, that enzyme instability may occur in a formulation, again for reasons presently not fully understood.

Claims: A magnesium sulfate stabilized peracid and enzyme bleaching composition, said peracid and magnesium sulfate combined in a discrete granule the peracid having the structure wherein R is C₄₋₂₀ alkyl, in which maximum enzyme stability is achieved when the total water present in said granule is restricted to an amount of 50 to 70% of the weight of magnesium sulfate used to control exothermic decomposition, and the weight ratio of magnesium sulfate: peracid is less than 1:1. A composition as claimed in claim 1 characterized in that the ratio by weight of magnesium sulfate to diperoxydodecanedioic acid is maintained between 0.15:1 and 0.9:1, preferably between 0.35 and 0.75:1. A composition as claimed in claim 1 characterized in that the granule comprises: i) 0.5 to 50% by weight peracid; and ii) 0.025% to 45% by weight magnesium sulfate used as an exotherm control agent; and the composition contains 0.1 to 10%, by weight enzymes. A composition as claimed in any of claims 1 to 3 characterized in that the peracid is a discrete particulate diperacid capable of delivering in aqueous solution about 0.1 to 50 ppm A.O. A composition as claimed in any of claims 1 to 4 characterized in that the peracid is diperoxydodecanedioic acid. A composition as claimed in any of claims 1 to 5 characterized in that at least one enzyme is a hydrolase. A composition as claimed in any of claims 1 to 6 characterized in that at least one enzyme is selected from the group consisting essentially of proteases, amylases, lipases, cellulases and mixtures thereof. A composition as claimed in claim 7 characterized in that at least one enzyme is an alkaline protease. A composition as claimed in any of claims 1 to 8 characterized in that the water content does not exceed about 65% of the level of magnesium sulfate present in the composition. A composition as claimed in any of claims 1 to 9 characterized in that it further includes selected adjuncts from the group consisting essentially of fluorescent whitening agents, bluing agents, fillers, builders, surfactants, pH adjusters and mixtures thereof. A composition as claimed in claim 10 characterized in that the pH adjuster is boric acid. A composition according to any one of the preceding claims characterized in that the granules contain an unneutralized polymeric acid as binder, preferably an unneutralized polyacrylic acid. A composition as claimed in claim 12 characterized in that the granules contain a dicarboxylic acid and sodium sulphate, and the unneutralized polymeric acid has a pH of less than 3 in aqueous solution. A method of stabilizing a peracid bleaching composition containing a peracid which has the structure wherein R is C₄₋₂₀ alkyl and magnesium sulfate within a discrete granule and enzyme wherein the weight ratio of magnesium sulfate to peracid is less than 1:1 comprising controlling the amount of water present in the composition such that it falls within the range of 50-70% of the magnesium sulfate present in the composition for exotherm control purposes.

Inventors: COYNE THOMAS S, HAENDLER BLANCA L, KLAPPROTT DANIEL H, LUTKIN ERIC A, MITCHELL FRANCES E, RIGGIN UTE H, STEICHEN DALE S, THOMPSON SUZANNE M, COYNE, THOMAS S., HAENDLER, BLANCA L., KLAPPROTT, DANIEL H., LUTKIN, ERIC A., MITCHELL, FRANCES E., RIGGIN, UTE H., STEICHEN, DALE S., THOMPSON, SUZANNE M.
Applicants: CLOROX CO, THE CLOROX COMPANY
Application year: 1986
Main classification: C11D3
IPC codes: C11D3