Hydrolytic enzyme composition and bleaching compositions containing them

Abstract: Methods and compositions for increasing stability of enzymes in oxidant dry bleach are disclosed. Enzyme stability is adversely affected by increased temperature, humidity, and the presence of strong oxidants, such as peracids. The invention provides enzyme stability in the presence of oxidant bleaches by coating or encapsulating the enzyme, while providing enzyme solubility suitable for use in bleach mixtures upon introduction to an aqeuous medium. Particularly, alkali and neutral materials act as protection agents, which neutralize oxidant species before they contact and denature the enzyme. Other standard bleaching composition adjuncts such as builders, fillers, buffers, brighteners, fragrances may be included in the enzyme-containing oxidant bleach composition in addition to the discrete coated enzyme granules.

Description: This invention relates to household fabric bleaching products, and more particularly to dry bleach products which are based upon oxidant bleaches, especially organic peroxyacid bleach compositions, and which contain enzymes. The enzymes are present in the bleach composition as discrete granules which are coated to enhance the stability of the enzymes. The enzyme coating contains one or more active agents which protect the enzyme from degradation by the bleach composition. Related applications are EP-A-0214789 and EP-A-0212976. Bleaching compositions have long been used in households for the bleaching and cleaning of fabrics. Liquid bleaches based upon hypochlorite chemical species have been used extensively, as they are inexpensive, highly effective, easy to produce, and stable. However, the advent of modern synthetic dyes and the use of modern automatic laundering machines have introduced new requirements in bleaching techniques, and have created a need for other types of bleaching compositions. In order to satisfy this need, and to broaden and extend the utility of bleaches in household use, other bleach systems have been introduced in recent years. Of particular interest recently have been dry bleaching compositions based upon peroxyacid chemical species. Peracid chemical compositions have a high oxidation potential due to the presence of one or more of the chemical functional group: In addition to active oxidizing agents, it is also desirable to provide one or more enzymes for the purpose of stain removal. Enzymes have the ability to degrade and promote removal of certain soils and stains by the cleavage of high molecular weight soil residues into low molecular weight monomeric or oligomeric compositions readily soluble in cleaning media, or to convert the substrates into different products. Enzymes have the substantial benefit of substrate specificity: enzymes attack only specific bonds and usually do not chemically affect the material to be cleaned. Examples of such enzymes are those selected from the group of enzymes which can hydrolyze stains and which have been categorized by the International Union of Biochemistry as hydrolases. Grouped within the hydrolases are proteases, amylases, lipases, and cellulases. Enzymes are somewhat sensitive proteins which have a tendency to denature (change their molecular structures) in harsh environments, a change which can render the enzymes ineffective. Strong oxidant bleaches such as organic peracids adversely affect enzyme stability, especially in warm, humid environments in which there is a concentration of oxidant bleaching species. Various methods to stabilize enzymes and provide a good mixture of enzyme and detergent or bleach have been proposed. Enzymes have variously been attached to carriers of clay, starch, and aminated polysaccharides, and even coglutinated to detergent carriers. Enzymes have been granularized, extruded, encased in film, and provided with colorizing agents. Attempts have been made to enhance enzyme stability by complexing the enzymes with proteins, by decreasing the relative humidity of the storage environment, by separating the bleach into discrete granules, and by the addition of reducing agents and pH buffers. However, the instability of enzymes in peroxyacid bleach compositions has continued to pose a difficulty, especially in the long-term storage of peroxyacid bleach compositions in which enzymes and bleach are in intimate contact. In EP-A-0,206,417 there is disclosed a bleaching composition comprising diperoxydodecanedioic acid bleach granulate and a coated granulate enzyme composition comprising an enzyme core having a protease activity and a protective coating surrounding said core, said protective coating containing an alkaline buffer salt having a pH of up to 11, sodium sulfite as anti-oxidant, a water-soluble overcoating such as polyethylene glycol or tallow alcohol condensed with 22 moles of ethylene oxide and optionally a cellulose filler; this specification also discloses a method for rendering enzymes stable during long term storage in the presence of said bleach granulate and a process for the preparation of said bleaching and enzyme compositions. In FR-A-2,066,844 there is disclosed a process for the preparation of a granulate enzyme product comprising an enzyme in the form of granulates and sodium silicate added after the granulation and a water-soluble polymer carrier. Other references of interest are BE-A-0,838,125 and NL-A-7,411,994. The disclosures of EP-A-0,277,532 and EP-A-0,286,773 published after the filing date of the application are also mentioned. The present invention relates to a soluble hydrolytic enzyme composition as well as to a bleaching composition containing an organic diperacid and the said enzyme composition. The invention therefore provides a soluble hydrolytic enzyme composition, adapted to be formulated with a bleach-containing composition, said hydrolytic enzyme composition comprising: a core including hydrolytic emzyme, and a coating layer encapsulating said core, said coating layer including a protective agent which reacts with and neutralizes enzyme-deactivating oxidant species, said protective agent being either: (a) an alkali metal silicate; (b) an alkali metal silicate with an additional additive selected from the group consisting of an antioxidant, a reducing agent or a transition metal; or (c) a water-soluble polymer and an additive which is selected from the group consisting of a transition metal or a reducing agent; or (d) a mixture thereof. In addition the invention provides a bleaching composition containing an oxidant bleach and enzyme granules, in which enzyme stability is prolonged without undue loss of solubility despite intimate contact of said enzyme granules and said oxidant bleach, comprising: (a) an organic peracid with the structure wherein R is C₄-₂₀ alkyl; and (b) a hydrolase which is coated by a protective agent which reacts with and neutrilizes enzyme-deactivating oxidant species, said protective agent being either: (a) an alkali metal silicate; (b) an alkali metal silicate with an additional additive selected from the group consisting of an antioxidant, a reducing agent or a transition metal; or (c) a water soluble polymer and an additive which is selected from the group consisting of a transition metal or a reducing agent; or (d) a mixture thereof. The compositions provide enzyme stability during prolonged storage in the presence of oxidants while supporting enzyme stability. The improved enzyme composition is prepared by coating or encapsulating the enzyme or enzymes with a material which both effectively renders the enzyme resistant to degradation in bleach products and allows for sufficient solubility upon introduction into an aqueous medium, such as found during laundering. The materials of the coating layer act as protective agents, which neutralize oxidant species before they contact and denature the enzyme. Thus sodium silicate physically blocks the attack of the enzyme by oxidants, and chemically neutralizes the oxidants. Reducing agents, such as sodium sulfite and sodium thiosulfite, and antioxidants such as BHT (butylated hydroxytoluene) and BHA (butylated hydroxyanisole), which act to inhibit radical chain oxidation. Transition metals, especially iron, cobalt, nickel, and copper act as catalysts to speed up the breakdown of oxidant species and thus protect the enzymes. Reducing agents and transition metals are also used in conjunction with water-soluble polymers, which do not of themselves protect the enzyme, but which provide enhanced solubility and act as dispersant agents for protective agents. Standard bleaching composition adjuncts such as builders, fillers, buffers, brighteners, fragrances, and the like may be included in an enzyme-containing oxidant bleach composition in addition to the discrete enzyme granules, and the oxidant bleach. Brief Description of the Drawings Figure 1 is a scanning electron micrograph showing a cross-sectional view of uncoated Alcalase (TM) 2.OT. Figure 2 is a scanning electron micrograph showing a cross sectional view of Alcalase (TM) 2.OT which has been coated with sodium silicate having a modulus (ratio SiO₂:Na₂O) of 2.00, to a weight gain of 25.5%. Figure 3 is a cross-sectional diagram of an enzyme granule or prill which includes a core carrier material, an enzyme layer, and a de-dusting film. Figure 4 is a cross-sectional diagram of an enzyme granule such as that shown in Figure 3 which has been coated with a protective coating according to the subject invention. Detailed Description of the Invention Unless indicated to the contrary, all percentages, ratios, or parts are determined by weight. ENZYMES Enzymes are a known addition to conventional and perborate-containing detergents and bleaches, where they act to improve the cleaning effect of the detergent by attacking soil and stains. Enzymes are commercially supplied in the form of prills, small round or acicular aggregates of enzyme. A cross-section of a prilled enzyme is shown in Figure 1. When such prills were added to traditional dry detergents the enzyme tended to settle out from the remainder of the detergent blend. This difficulty was solved by granulation of the enzyme, i.e., by adhering the enzyme to a carrier, such as starch or clay, or by spraying the enzyme directly onto the solid detergent components. Such techniques were adequate for the relatively mild dry detergent and detergent bleach compositions known in the past. However, these granulation techniques have not proved to be adequate to protect enzymes from degradation by newer, stronger oxidant bleach compositions. Enzymes capable of hydrolyzing substrates, e.g., stains, are commonly utilized in mild bleach compositions. Accepted nomenclature for these enzymes, under the International Union of Biochemistry, is hydrolases. Hydrolases include, but are not limited to, proteases (which digest proteinaceous substrates), amylases (also known as carbohydrases, which digest carbohydrates), lipases (also known as esterases, which digest fats); cellulases (which digest cellulosic polysaccharides), and mixtures thereof. Proteases, especially alkalkine proteases, are preferred for use in this invention. Alkaline proteases are particularly useful in cleaning applications, as they hydrolyze protein substrates rendering them more soluble, e.g., problematic stains such as blood and 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 trade names Esperase (TM) , Savinase (TM) , and Alcalase (TM) , from Novo Industri A/S, of Bagsvaerd, Denmark; those sold under the trade names Maxatase (TM) , and Maxacal (TM) , fromGist-Brocases N.V of Delft, Netherlands; and those sold under the trade names Milezyme (TM) APL, from Miles Laboratories, Elkart, Indiana. Mixtures of enzymes are also included in this invention. See also, US-A-4,511,490, issued to Stanislowski et al . Commercially available proteases are supplied as prilled, powdered or comminuted enzymes. These enzymes can include a stabilizer, such as triethanolamine, clays, or starch. Other enzymes may be used in the compositions in addition to, or in place of, proteases. Lipases and amylases can find use in the compositions. Lipases are described in US-A-3,950,277, column 3, lines 15-55. Suitable amylases include Rapidase®, from Societe Rapidase, France; Maxamyl®, from Gist-Brocases N.V. Termamyl®, from Novo Industri A/S and Milezyme® DAL, from Miles Laboratories. Cellulases may also be desirable for incorporation and description of exemplary cellulose are found in the specification of US-A-4,479,881, issued to Tai, US-A-4,443,355, issued to Murata et al , US-A-4,435,307, issued to Barbeagaard et al and US-A-3,983,002, issued to Ohya et al . The enzyme level content preferred for use in this invention is, by weight of the uncoated enzyme, about 0.1% to 10%, more preferably 0.25% to 3%, and most preferably 0.4% to 2%. OXIDANT BLEACHES Enzymes are subject to degradation by heat, humidity and chemical action. In particular, enzymes can be readily denatured upon contact with strong oxidizing agents. Generally, prior art techniques, e.g., granulation, may not be sufficient to protect enzymes in strong oxidant compositions, such as those based upon dry hypochlorite and peroxyacid bleaches. Oxidant bleaches generally deliver, in aqueous media, about 0.1 to 50 ppm A.O. (active oxygen), more generally about 0.5 to 30 ppm A.O. An analysis for, and a description of, A.O. appears in "Peracid and Peroxide Oxidations", Oxidation , pp. 213-258 (1969), by Dr. S.N. Lewis. Organic diperacids are good oxidants and are known in the prior art to be useful bleaching agents. The organic diperacids of interest can be synthesized from a number of long chain diacids. US-A-4,337,213, issued June 29, 1982 to Marynowski, et al , describes the production of peracids by the reaction of a selected acid with H₂O₂ in the presence of H₂SO₄. Organic diperacids have the general structure: where R is a linear alkyl chain of from 4 to 20, more preferably 6 to 12 carbon atoms. Particularly preferred are diperoxydodecanedioic acid (DPDDA), in which R is (CH₂)₁₀, and diperazelaic acid (DPAA) in which R is (CH₂)₇. Detergent bleaches which contain peroxyacids generally also contain exotherm control agents, to protect the peroxyacid bleach from exothermic degradation by controlling the amount of water which is present. Typical exotherm control agents are hydrated salts such as an MgSO₄/Na₂SO₄ mixture. It has been discovered that combining the peroxyacid and the exotherm control agents into granules, and carefully controlling the water content of such granules, increases the stability of the bleach granules as well as the stability of enzymes present in the composition. See EP-A-0212976. OTHER ADJUNCT INGREDIENTS Adjunct ingredients may be added to the bleach and enzyme composition disclosed herein, as determined by the use and storage of the product. Bleaching compositions are disclosed in EP-A-0212976. Organic dicarboxylic acids of the general formula HOOC-R-COOH, wherein R is 1 to 10 carbon atoms (for instance, adipic acid R = (CH₂)₄), are desirable adjuncts in the detergent bleach composition. Such organic acids serve to dilute the diperacid, if present, and aid in pH adjustment of the wash water when the bleach product is used. When the diperacid is present in a granular form with the exotherm control agent and, optionally, with organic acids, it is especially desirable to maintain the physical integrity of the granule by the use of binding agents. Such materials serve to make the bleach granules resistant to dusting and splitting during transportation and handling. Unneutralized polymeric acids are of particular interest, as their use greatly reduces or eliminates the unpleasant odor note associated with diperoxyacids in detergent bleach compositions. Fluorescent whitening agents (FWAs) are desirable components for inclusion in bleaching formulations, as they counteract the yellowing of cotton and synthetic fibers. FWAs are adsorbed on fabrics during the washing and/or bleaching process. FWAs function by adsorbing ultraviolet light, which is then emitted as visible light, generally in the blue wavelength ranges. The resultant light emission yields a brightening and whitening effect, which counteracts yellowing or dulling of the bleached fabric. Such FWAs are available commercially from sources such as Ciba Geigy Corp. of Basel, Switzerland, under the trade name "Tinopal". Similar FWAs are disclosed in US-A-3,393,153, issued to Zimmerer et al ., which disclosure is incorporated herein by reference. Protection of the FWAs may be afforded by mixing with an alkaline diluent, which protects the FWAs from oxidation; a binding agent; and, optionally, bulking agents e.g., Na₂SO₄, and colorants. The mixture is then compacted to form particles, which are admixed into the bleach product. The FWA particles may comprise from about 0.5% to 10% by weight of the bleach product. A fragrance which imparts a pleasant odor to the bleaching composition is generally included. As fragrances are subject to oxidation by bleaches, they may be protected by encapsulation in polymeric materials such as polyvinyl alcohol, or by absorbing them into starch or sugar and forming them into beads. These fragrance beads are soluble in water, so that fragrance is released when the bleach composition is dissolved in water, but the fragrance is protected from oxidation by the bleach during storage. Fragrances also are used to impart a pleasant odor to the headspace of the container housing the bleach composition. See, for example, EP-A-0258991. Buffering, building, and/or bulking agents may also be present in the bleach product. Boric acid and/or sodium borate are preferred agents to buffer the pH of the composition. Other 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 organic builders such as sodium sulfosuccinate. Bulking agents may also be included. The most preferred bulking agent is sodium sulfate. Buffer, builder and bulking agents are included in the product in particulate form such that the entire composition forms a free-flowing dry product. Buffers may range from about 5% to 90% by weight of the composition. COATED ENZYMES Coated enzymes are prepared by coating or encapsulating the enzyme with a material which both effectively renders the enzyme resistant to the oxidation of bleach, and allows for sufficient solubility upon introduction of the granule into an aqueous medium. Active agents which protect the enzyme when included in the coating fall into several categories: alkali metal silicates optionally with an additional additive which is an antioxidant or a reducing agent or a transition metal and a water-soluble polymer with a transition metal or a reducing agent. Mixtures of such additives may be used. The most preferred coatings provide a physical barrier to attack by oxidants, and also provide a chemical barrier by actively neutralizing scavenging oxidants. Alkali metal silicates, especially sodium silicate, and combinations of such silicates with alkali metal carbonates or bicarbonates, especially sodium carbonate, provide such preferred coatings. Silicates, or mixtures of silicates with carbonates or bicarbonates, appear especially desirable since they form a uniform glassy matrix when an aqueous dispersion of the silicate, or mixtures of silicates with carbonates or bicarbonates, is applied to the enzyme core. This obviates the need for a carrier material to effect coating. The addition of the alkali metal carbonates or bicarbonates can improve the solubility of the enzyme coating. The levels of such carbonate or bicarbonate in the silicate coating can be adjusted to provide the desired stability/solubility characteristics. The pH of a salt, or mixtures thereof, is measured as a 10% aqueous solution of the salt or salts. Other preferred coatings include an alkali metal silicate, as above, in conjunction with one or more other active agents which chemically react to neutralize any oxidant with which it comes in contact. In addition to the alkaline materials discussed above, active agents include reducing materials, i.e., sodium sulfite and sodium thiosulfite; antioxidants, i.e., BHA and BHT; and transition metals, especially iron, cobalt, nickel, and copper. These agents may be used singly, in combination with other reactive agents, or may be used in conjunction with carriers, especially film-forming water-soluble polymers, which do not of themselves provide enhanced enzyme stability, but which provide enhanced solubility for the active agents. When the active agents are provided in an essentially inert carrier, they provide active protection for the enzyme. Materials which may be used as active agents herein provide effective barriers to scavenging oxidant species by various means. Basic additives, such as sodium carbonate and sodium silicate, neutralize acidic oxidants. Reducing agents, such as sodium sulfite and sodium perborate tetrahydrate, and antioxidants, such as BHA and BHT, reduce the effect of scavenging oxidant species by chemical reaction with the oxidants. The transition metals (i.e., iron, cobalt, nickel, copper, and mixtures thereof) act to catalyze the decomposition of the oxidant and thus protect the enzyme. Reducing agents, antioxidants, and transition metals may be used in the enzyme coating either in conjunction with an alkali metal silicate or in conjunction with an appropriate carrier. Suitable carriers for the active agents herein need not provide for stability of the enzyme without the presence of the active agents, but they must be sufficiently non-reactive in the presence of the protective active agents to withstand decomposition by the oxidant bleaches. Appropriate carriers include water-soluble polymers, surfactants/dispersants, and basic materials. Examples of water-soluble polymers include polyacrylic acid (i.e., Alcosperse 157A), polyethylene glycol (i.e., Carbowax PEG 4600), polyvinyl alcohol, polyvinylpyrrolidone and Gantrez ES-255 (TM) (monoethyl ester of poly (methyl vinyl ether/maleic acid)). Exemplary of the surfactants which fine use as carriers are wetting agents such as Neodol (TM) 25-12 and 45-7, and polyoxyethylene stearyl ether (i.e., Brij 700 (TM) ), both of which are nonionic surfactants. When the alkali metal silicates are used as protective active agents, care must be taken to provide sufficient solubility. The modulus of the silicate determines its solubility in aqueous media. Sodium silicate having a modulus (i.e., ratio of SiO₂:Na₂O) of 3.22:1, such as PQ brand "N" sodium silicate provides adequate enzyme stability, but low solubility under U.S. washing conditions. Sodium silicate having a modulus of 2:1, such as PQ brand "D" sodium silicate provides both acceptable stability and sufficient solubility. Preferred for use in the invention is sodium silicate having a modulus of about 1:1 to 3:1, more preferably about 1:1 to 2.75:1; most preferably, 1.5:1 to 2.5:1, if no other additive to the coating is present. However, sodium silicates with a modulus of greater than 3:1 may be utilized, particularly when combined with an additive such as a reducing agent, for example, sodium sulfite. It is believed that the additive modifies the crystalline structure of the silicate, rendering the coating more soluble. The alkali metal silicates or carbonates may be used in conjunction with a water-soluble carrier to ensure sufficient solubility. Mixtures of the alkali metal silicates and/or the alkali metal carbonates may be used. In the most preferred embodiment, sodium silicate may be present in the coating in an amount of 5 to 100% by weight, preferably from 40 to 100%, more preferably 60 to 100% by weight. Lithium or potassium silicates may be present in the coating in an amount of 5 to 100% by weight, preferably 40 to 100%, more preferably 60 to 100% by weight. Similarly, sodium carbonate may be present in the coating in an amount of 0 to 99% by weight, preferably from 2 to 50%, more preferably 4 to 25% by weight. Lithium or potassium carbonates may be present in the coating in an amount of 0 to 99% by weight, preferably 2 to 50%, more preferably 4 to 25% by weight. Other protective active agents provide varying solubilities and varying stabilizing effects. It appears that transition metals may cause decomposition of the peracid in the wash solution if present in more than small amounts. It is therefore generally preferred that transition metals be present in the coating in an amount of 1 to 2000 parts per million, preferably 2 to 1000, more preferably 50 to 500 parts per million. Reducing agents do not catalytically decompose the peracid, so that they may be present in the coating in amounts of 0.1 to 60% by weight, preferably 1 to 50%, more preferably 2 to 40% by weight. Similarly, antioxidants do not catalytically decompose the peracid, and may be present in the coating in amounts of 0.1 to 20 percent by weight, generally 0.5 to 15, more usually 0.75 to 10 weight percent. Variation of the concentration of active agents to facilitate solubility will be apparent to those skilled in the art. A discussion of the interaction of transition metals and oxidant species may be found in M.W. Lister, Canadian Journal of Chemisty, 34:479 (1956), and K. Hayakawa et al., Bulletin of the Chemical Society of Japan , 47:1162. The amount of protective active agents which are required to protect the enzyme will depend in part upon the nature of the oxidant bleach, upon the temperature and relative humidity of the environment, and the expected length of time for storage. Additionally, the amount of protective active agent which is required in the coating will vary with the type of protective agent or combination of protective agents used. Basic materials such as alkali metal silicates may be present in amounts as little as 5% by weight, may constitute a majority of the coating, or may be used as the sole coating. Reducing agents may be present in the coating material from 0.1 to 60 percent by weight, generally 1 to 50, more usually 2 to 40 weight percent. Antioxidants may be present in the coating material from 0.1 to 20 percent by weight, generally 0.5 to 15, more usually 0.75 to 10 weight percent. Transition metals may be present in the coating material at a concentration of 1 to 2000 parts per million, generally 2 to 1000 ppm, more usually 50 to 500 ppm. Especially preferred is a coating of sodium silicate with or without sodium carbonate in which transition metals are present at a concentration of 50 to 500 parts per million. Enzymes may be coated in any physical form. Enzyme prills, which are commonly provided commercially, provide a particularly convenient form for coating, as they may be fluidized and coated in a fluid-bed spray coater. Figure 1 is a scanning electron micrograph cross-section of an enzyme prill. Figure 3 shows another form in which enzymes are commercially available, including a core carrier material, 1, the enzyme layer, 2, and a film layer, 3, which acts to minimize dusting characteristics of the enzyme. Coating in a fluid-bed spray coater provides good coating of the granule while allowing economical use of the reactive agents. Enzymes, in prill form or other forms, may be coated, for example, by mixing, spraying, dipping, or blotting. Other forms of coating may be appropriate for other enzyme forms, and will be readily apparent to those skilled in the art. Where necessary, a wetting agent or binder such as Neodol (TM) 25-12 or 45-7 may be used to prepare the enzyme surface for the coating material. Figure 2 is a scanning electron micrograph which shows an enzyme prill, 2, which has been coated with PQ brand "D" sodium silicate. The coating, 4, comprises approximately 25.5% by weight of the uncoated granule. The enzyme granule of Figure 2 was coated using an Aeromatic (TM) fluid bed, Model STREA-1, using a flow rate of 5g/min, a fluidizing air rate of 130m³/h, an atomizing air pressure of 1.3 bar, and a bed temperature of 55°C. The coating which was atomized consisted of 15% sodium silicate and 85% water. The average coating thickness is approximately 14 µm. Figure 4 is a diagrammatic cross-section demonstrating an enzyme such as shown in Figure 3 which has been coated with a soluble protective coating, 4, according to the subject invention. The thickness of the coating will, to some degree, depend upon the procedure used to apply the coating. When enzyme prills were coated with a "D" sodium silicate solution to a 15% weight gain, the coating averaged approximately 10 µm in thickness. When the same enzyme prills were coated with the same coating to a weight gain of 25%, the coating averaged approximately 14 µm in thickness. Generally, the coating will comprise about 3 to 500% or more by weight of the uncoated enzyme, preferably 5 to 100%, more preferably 10 to 40%, most preferably 15 to 30% by weight. It is obvious that increased coating thickness will decrease enzyme solubility for any given coating. It is therefore desirable to provide a coating which substantially completely coats or encapsulates the granule, which is uniform and durable, easy to apply, causes little or no agglomeration of the coated granules, and which yields adequate solubility in aqueous media, while suitably protecting the activity of the enzyme. Suitable protection of the enzyme herein refers to the percentage of active enzyme remaining after it has been in intimate contact with an oxidant bleach within a closed environment. As high heat and high relative humidity increase enzyme denaturation, enzyme stability is conveniently measured at 32°C (90°F) and 85% relative humidity. Suitable stability is provided by a coating when the stability of a coated enzyme is at least two times, preferably four times, and more preferably five or more times greater than the amount of active uncoated enzyme remaining under the experimental conditions after at least two weeks, more preferably after four or more weeks. Experimental conditions involve an admixture of enzyme with a peroxyacid bleach formulation having at least 20% by weight DPDDA granules which are comprised of 20% DPDDA, 9% MgSO₄, 10% adipic acid, and 1% binding agent, the remainder being Na₂SO₄ and water. The coated enzyme granules must provide sufficient solubility in detergent solution that enzymes are readily released under wash conditions. A standard detergent solution may be made by dissolving 1.5 grams of Tide (TM) (Procter and Gamble) in one liter of water of 20°C. In general, 90% of the discrete enzyme-containing coated granules should dissolve, disperse or disintegrate in detergent solution at about 20°C within about 15 min., preferably within about 12 min., and more preferably within about 8 min. The coated enzymes find use in oxidant bleach compositions. Typical formulations for such bleach compositions are as follows:- EXAMPLE A Component Wt. % Peracid Granules 1-80 pH Control Particles (boric acid) 1-50 Coated Enzyme Granules (by weight of uncoated enzyme) 0.1-10 FWA particles 0.5-10 Fragrance beads 0.1-2 Bulking Agents (Na₂SO₄) remainder EXAMPLE B Component Wt.% Peracid Granules 10-50 pH Control Particles (boric acid) 10-40 Coated Enzyme Granules (by weight of uncoated enzyme) 0.5-4 FWA particles 0.5-5 Fragrance beads 0.1-1 Bulking Agent (Na₂SO₄) remainder EXAMPLE C Component Wt. % DPDDA 5-15 Boric Acid 7-20 FWA 0.1-1 Coated Enzyme Granules (by weight of uncoated enzyme) 0.3-2 Na₂SO₄ remainder The above formulations are only illustrative. Other formulations are contemplated, so long as they fall within the guidelines for the oxidant bleach/coated enzyme compositions of the invention. The weight percent of the coated enzyme granules in the formula will vary significantly with the weight of the coating. It is intended that the amount of enzyme in the formula falls generally within the range of 0.1 to 10% by weight of the uncoated enzyme. A preferred embodiment provides a bleach composition in which a peracid bleach is found in stabilized granules in which the water content is carefully controlled, according to EP-A-0212976. The peracid granules and the discrete enzyme granules are each dry-mixed with the other components to yield a dry bleach composition containing coated enzyme granules. EXPERIMENTAL The alkali metal silicate coating provides a soluble shell substantially enclosing the enzyme, which protects the enzyme from the oxidant bleach. The use of additional protective active agents in this coating may increase or decrease the stability or solubility of the coated enzyme. Similarly, the presence of protective agents in a carrier may vary the solubility of the enzyme granule, but will increase the stability of the enzyme as compared to the carrier alone. The table which follows demonstrates the stability and solubility of various silicates, carriers, and reactive additives. COATED ENZYME STABILITIES AND SOLUBILITIES Coatings Stability (% Enzyme Remaining at 32°C (90°F)/85%RH) Solubility (Time to dissolve in minutes) 2 wks 3 wks 4 wks 50% 90% 1. Uncoated 7.4 9.4 4.2 1 3 2. "N"/metals 78.2 49.5 23.6 NM NM 3. "N"/Na₂SO₃ 65.3 48.8 7.6 1.5 3 4. "D" 95.4 73.8 73.8 2 4.5 5. "D"/metals 75.5 88.3 87.4 2.5 5 6. "D"/Na₂CO₃ 87.5 69.9 65.6 1.5 3.5 7. "D"/Na₂S0₃ 92.5 91.3 68.4 2 3 8. PVA 73.3 18.2 3.6 1 2 9. PVA/BHT 74.4 83.7 32.1 NM NM NM = not measured "N" = sodium silicate, modulus = 3.22, i.e., PQ brand "N" sodium silicate; "D" = sodium silicate, modulus = 2, i.e., PQ brand "D" sodium silicate; PVA = poly vinyl alcohol Solubility was determined in each case in a standard detergent solution of one liter of water to which 1.5 grams of Tide (TM) (Procter and Gamble) has been added. 20 ppm of enzyme in solution was tested. The weight of the uncoated enzyme was adjusted according to the weight gain of the coating. Stirring was continued while aliquots were removed. Three cc aliquots were removed from solution at 15 second intervals for the first minute, and thereafter at 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 6, 8, 10, 12, 15, 20, 25 and 30 minutes. An uncoated control was run with each set of coated samples to ensure consistency of values. Stability was analyzed as follows: a one-liter volumetric flask was filled two-thirds full with 0.05M borate buffer. Four mL 1.5M Na₂SO₃ was added to quench DPDDA. If foaming occurred, additional quencher was added 1 cc. at a time, as necessary. Ten grams of sample was added, rinsing the sides with borate buffer, stirring for 10 minutes. The mixture was then diluted to 1L with borate buffer and stirring was continued for 5 minutes. Eight cc of the solution was pipetted into a vial and 8 cc additional buffer was added. This yields 0.075g Alcalase (TM) per liter of buffer. Three cc of the diluted solution was pipetted into a Scientific auto-analyzer for each sample analyzed. Unless otherwise noted, stability of the sample was determined after the coated enzyme was admixed with peroxyacid bleach composition containing 20% DPDDA granules. The mixture was then stored in sealed 4 oz. Double Poly Coated cartons. Enzyme granules were coated using an Aeromatic (TM) fluid bed, Model STREA-1, using a flow rate of 5g/min, a fluidising air rate of 130m³/h, an atomizing air pressure of 1.3 bar, and a bed temperature of 55°C. "D" and "N" sodium silicates refer to "D" and "N" sodium silicate, from PQ corp. EXAMPLE 1 Enzymes and a diperoxyacid detergent bleach composition were each placed within a closed container, but not in physical contact with each other. A 0.15 grams Alcalase 2.0T sample was placed in an open 20 cc vial. The vial was then placed within an 216.90g (8-oz) jar which contained a diperoxyacid bleach composition according to Example "C" above. The 216.90g (8-oz). jar was then sealed, and stored at 38°C (100°F) for four weeks. The enzyme activity after four weeks was 53% that of the original level. A control sample of Alcalase 2.0T stored at 38°C (100°F) for four weeks in a closed vial demonstrated enzyme activity of 97% of the original level. This demonstrates that mere physical separation was not sufficient to protect the enzyme from the effects of close proximity to the diperoxyacid bleach composition. Thus, active agents to protect the enzyme are required to achieve acceptable stability. EXAMPLE 2 Shellac was used to coat a hydrolase enzyme. Two hundred grams of Alcalase 2.0T was introduced into a fluid-bed spray coater and fluidized therein, by means of a stream of warm (50-55°C) air at approximately 100m³/h. A solution of shellac was diluted to 18% solids with ethanol, and was sprayed onto the fluidized enzyme through a nozzle, at a rate of 6 to 10g/min. The temperature prevailing in the turbulent air mixer was about 45°C. The readily flowable granulated enzyme composition was then coated. The coated enzymes were characterised as follows: The coating comprised 22% by weight of the uncoated enzyme. The granules demonstrated 50% solubility in detergent solution by 20 minutes at 20°C, and 90% solubility by 27 minutes. The stability of the coated enzyme in a diperoxyacid bleach composition was 46% of enzyme remaining at 32°C (90°F)/85% relative humidity after two week storage. The stability of the uncoated enzyme under the same conditions was 7.4%. This demonstrates that acceptable stability can be achieved but unless the coating is carefully selected, unacceptable solubility results. EXAMPLE 3 Polyethylene glycol was used to coat a hydrolase enzyme. Two hundred grams of Alcalase 2.0T was introduced into a fluid-bed spray coater and fluidized therein, by means of a stream of warm (50-55°C) air at approximately 130m³/h. A solution of 20% PEG 4600 Carbowax (TM) (Union Carbide), 30% water, and 50% ethanol was sprayed onto the fluidized enzyme through a nozzle at a rate of 3g/min. The temperature prevailing in the turbulent air mixer was about 45°C. The readily flowable granulated enzyme composition was then coated. The coated enzymes were characterised as follows: The coating comprised 20.6% by weight of the uncoated enzyme. The granules demonstrated 50% solubility in detergent solution by 0.75 minutes at 20°C, and 90% solubility by 1.5 minutes. The stability of the coated enzyme in a diperoxyacid bleach composition was 13.8% of enzyme remaining at 32°C (90°F)/85% relative humidity after two week storage. The stability of the uncoated enzyme under the same conditions was 7.4%. This demonstrates that mere physical separation is not sufficient to protect the enzyme from oxidant species. A chemical barrier which both acts to neutralize the oxidant species and which provides suitable solubility for the detergent bleach is required. EXAMPLE 4 Four parts (by weight) of Alcalase 2.0T was added in a beaker to one part Neodol 45-7 (Shell) at 38°C (100°F). Sodium carbonate was added one part at a time with vigorous stirring to a total of eight parts of sodium carbonate. The percent weight gain was approximately 225% based upon the weight of the enzyme. After 4 weeks at 38°C (100°F)in a dry bleach formula containing approximately 20% peracid granules the stability of the coated enzyme was 83%, compared to 67% for the uncoated enzyme under the same conditions. EXAMPLE 5 Sodium silicate having a modulus of 2.00 was used to coat a hydrolase enzyme. Two hundred g of Alcalase 2.0T was introduced into a fluid-bed spray coater and fluidized therein, by means of a stream of warm (50-55°C) air at approximately 130m³/h. "D" sodium silicate solution, diluted with water from 44% solids to 25% solids, was sprayed onto the fluidized enzyme through a nozzle, at a rate of 7g/min. The temperature prevailing in the turbulent air mixer was about 50°C. The readily flowable granulated enzyme composition was then coated. The coated enzymes were characterised as follows: The coating comprised 22.5% by weight of the uncoated enzyme. The granules demonstrated 50% solubility in detergent solution by 2 minutes at 20°C, and 90% solubility by 4.5 minutes. The stability of the coated enzyme in a diperoxyacid bleach composition was 74% of enzyme remaining at 32°C (90°F)/85% relative humidity after four weeks storage. The stability of the uncoated enzyme under the same conditions was 4%. EXAMPLE 6 Transition metals were added to the sodium silicate of Example 5. 200g of Alcalase 2.0T was introduced into a fluid-bed spray coater and fluidized therein, by means of a stream of warm (50-55°C) air at approximately 130m³/h. "D" sodium silicate solution containing 100 ppm each of copper as copper sulfate, iron as iron sulfate, cobalt as cobalt sulfate, and nickel as nickel sulfate, was sprayed onto the fluidized enzyme through a nozzle at a rate of 6g/min. The temperature prevailing in the turbulent air mixer was about 50°C. The readily flowable granulated enzyme composition was then coated. The coated enzymes were characterised as follows: The coating comprised 22% by weight of the uncoated enzyme. The granules demonstrated 50% solubility in detergent solution by 2.5 minutes at 20°C, and 90% solubility by 5.0 minutes. The stability of the coated enzyme in a diperoxyacid bleach composition was 87% of enzyme remaining at 32°C (90°F)/85% relative humidity after four week storage. The stability of the uncoated enzyme under the same conditions was 4%. EXAMPLE 7 Sodium carbonate was added to the sodium silicate of Example 5. 200g. of Alcalase 2.0T was introduced into a fluid-bed spray coater and fluidized therein, by means of a stream of warm (50-55°C) air at approximately 130m³/h. A solution of 15% "D" sodium silicate solids, 10% Na₂CO₃, and 75% water was sprayed onto the fluidized enzyme through a nozzle, at a rate of 6g/min. The temperature prevailing in the turbulent air mixer was about 50°C. The readily flowable granulated enzyme composition was then coated. The coated enzymes were characterised as follows: The coating comprised 20.5% by weight of the uncoated enzyme. The granules demonstrated 50% solubility in detergent solution by 1.5 minutes at 20°C, and 90% solubility by 3.5 minutes. The stability of the coated enzyme in a diperoxyacid bleach composition was 66% of enzyme remaining at 32°C (90°F)/85% relative humidity after four week storage. The stability of the uncoated enzyme under the same conditions was 4% remaining. EXAMPLE 8 Sodium sulfite (a reducing agent) was added to the sodium silicate of Example 5. 200g. of Alcalase 2.0T was introduced into a fluid-bed spray coater and fluidized therein, by means of a stream of warm (50-55°C) air at approximately 130m³/h. Sodium sulfite was dissolved in water. It was then added to "D" sodium silicate to make a solution containing 12.6% "D" sodium silicate solids, 8.4% sodium sulfite, and 79% water. The solution was sprayed onto the fluidized enzyme through a nozzle, at a rate of 7g/min. The temperature prevailing in the turbulent air mixer was about 50°C. The readily flowable granulated enzyme composition was then coated. The coated enzymes were characterised as follows: the coating comprised 17% by weight of the uncoated enzyme. The coating was targeted to contain 60% "D" sodium silicate and 40% sodium sulfite. The granules demonstrated 50% solubility in detergent solution by 2 minutes at 20°C, and 90% by 3 minutes. The stability of the coated enzyme in a diperoxyacid bleach composition was 68% of enzyme remaining at 32°C (90°F)/85% relative humidity after four week storage. The stability of the uncoated enzyme under the same conditions was 4%. EXAMPLE 9 Sodium silicate having a modulus of 3.22 was used to coat a hydrolase enzyme. Solubility was significantly decreased as compared to sodium silicate having a modulus of 2.0. 200g. of Alcalase 2.0T was introduced into a fluid-bed spray coater and fluidized therein, by means of a stream of warm (45-50°C) air at approximately 130m³/h. "N" sodium silicate was diluted from 44% solids (as received) to 25% solids, with water. The solution was sprayed onto the fluidized enzyme through a nozzle, at a rate of 5g/min. The temperature prevailing in the turbulent air mixer was about 45°C. The readily flowable granulated enzyme composition was then coated. The coated enzymes were characterised as follows: The coating comprised 35% by weight of the uncoated enzyme. The granules demonstrated 50% solubility in detergent solution by 11.5 minutes at 20°C, and 90% solubility by 20 minutes. The stability of the coated enzyme in a diperoxyacid bleach composition was 64% of enzyme remaining at 32°C (90°F)/85% relative humidity after four week storage. The stability of the uncoated enzyme under the same conditions was 4%. EXAMPLE 10 Polyvinyl alcohol was used as a coating for a hydrolase enzyme. Solubility was good, however the stability of the enzyme was not acceptable after four weeks storage. Sodium lauryl sulfate was added to reduce tackiness. 200g. of Alcalase 2.0T was introduced into a fluid-bed spray coater and fluidized therein, by means of a stream of warm (40°C) air at approximately 130m³/h. A solution of 4.9% polyvinyl alcohol, 6.1% sodium lauryl sulfate, 44.5% water, and 44.5% ethanol was sprayed onto the fluidized enzyme through a nozzle, at a rate of 3g/min. The temperature prevailing in the turbulent air mixer was about 35-40°C. The readily flowable granulated enzyme composition was then coated. The coated enzymes were characterised as follows: The coating comprised 9% by weight of the uncoated enzyme. The granules demonstrated 50% solubility in detergent solution by 1 minute at 20°C, and 90% solubility by 2 minutes. The stability of the coated enzyme in a diperoxyacid bleach composition showed 3.6% of the enzyme remaining after four week storage at 32°C (90°F)/85% relative humidity. The stability of the uncoated enzyme under the same conditions was 4% remaining. EXAMPLE 11 When BHT, an antioxidant, was added to the PVA of Example 10, enzyme stability was significantly increased. 200g. of Alcalase 2.0T was introduced into a fluid-bed spray coater and fluidized therein, by means of a stream of warm (40°C) air at approximately 130m³/h. A solution containing 4.44% polyvinyl alcohol, 5.56% sodium lauryl sulfate, 0.1% BHT, 44.5% water and 44.9% ethanol was sprayed onto the fluidized enzyme through a nozzle, at a rate of 4g/min. The temperature prevailing in the turbulent air mixer was about 35-40°C. The readily flowable granulated enzyme composition was then coated. The coated enzymes were characterised as follows: The coating comprised 10.5% by weight of the uncoated enzyme. The coating was targeted to comprise 44% PVA, 55% sodium lauryl sulfate, and 1% BHT. The stability of the coated enzyme in a diperoxyacid bleach composition was 32% of enzyme remaining at 32°C (90°F)/85% relative humidity after four week storage. The stability of the uncoated enzyme under the same conditions was 4% remaining.

Claims: A soluble hydrolytic enzyme composition, adapted to be formulated with a bleach-containing composition, said hydrolytic enzyme composition comprising: a core including hydrolytic enzyme, and a coating layer encapsulating said core, said coating layer including a protective agent which reacts with and neutralizes enzyme-deactivating oxidant species, said protective agent being either: (a) an alkali metal silicate; (b) an alkali metal silicate with an additional additive selected from the group consisting of an antioxidant, a reducing agent or a transition metal; or (c) a water-soluble polymer and an additive which is selected from the group consisting of a transition metal or a reducing agent; or (d) a mixture thereof. A composition as claimed in claim 1 characterised in that the alkali metal silicate is selected from of sodium silicate, lithium silicate, potassium silicate, and mixtures thereof and an alkali metal carbonate is also optionally present. A composition as claimed in claim 1 or claim 2 characterised in that the hydrolytic enzyme is selected from proteases, amylases, lipases, cellulases, and mixtures thereof. A composition as claimed in any of claims 1 to 3 characterised in that the coating layer includes sodium silicate with a modulus of approximately 1:1 to 3:1. A bleaching composition containing an oxidant bleach and enzyme granules, in which enzyme stability is prolonged without undue loss of solubility despite intimate contact of said enzyme granules and said oxidant bleach, comprising: (a) an organic peracid with the structure wherein R is C₄-₂₀ alkyl; and (b) a hydrolase which is coated by a protective agent which reacts with and neutralizes enzyme-deactivating oxidant species, said protective agent being either: (a) an alkali metal silicate; (b) an alkali metal silicate with an additional additive selected from the group consisting of an antioxidant, a reducing agent or a transition metal; or (c) a water soluble polymer and an additive which is selected from the group consisting of a transition metal or a reducing agent; or (d) a mixture thereof. A composition as claimed in claim 5 further comprising an alkali metal carbonate in addition to the alkali metal silicate. A composition as claimed in claim 5 or claim 6 characterised in that the enzyme core is provided in the form of a prill, and said granule is produced by fluidizing said enzyme prill in a fluid-bed spray coater and spraying said coating onto said enzyme prill. A composition as claimed in any of claims 5 to 7 characterised in that the alkali metal silicate is selected from sodium silicate, lithium silicate, potassium silicate and mixtures thereof. A composition as claimed in any of claims 5 to 8 characterised on that the transition metal is selected from the group consisting of iron, cobalt, nickel, copper and mixtures thereof. A composition as claimed in any of claims 5 to 9 characterised in that the reducing agent is selected from sodium sulfite and sodium perborate tetrahydrate. A composition as claimed in any of claims 5 to 10 characterised in that the antioxidant is selected from BHT (Butylated hydroxytoluene) and BHA (butylated hydroxyanisole). A composition as claimed in any of claims 5-11 characterised in the said coating layer includes sodium silicate with a modulus of about 1:1 to 3:1. A composition as claimed in any of claims 5-12 characterised in that the solubility of said enzyme granule in detergent solution is at least 50% by 5 minutes at 20°C, preferably at least 90% by 12 minutes at 20°C. A composition as claimed in any of claims 5 to 13 characterised in that the stability of said enzyme granule is at least twice the stability of the uncoated enzyme in contact with said oxidant bleach at 32°C (90°F) and a relativehumidity of 85% after two weeks when said oxidant bleach is a peroxyacid bleach composition. A composition as claimed in any of claims 5 to 14 characterised in that the enzyme is a hydrolase selected from proteases, amylases, lipases, cellulases and mixture thereof, A composition as claimed in any of claims 5 to 15 characterised in that the diperoxyacid is diperoxydodecanedioic acid and or diperazelaic acid. A composition as claimed in any of claims 5 to 16 characterised in that the diperoxy acid is present in discrete granules. A composition as claimed in any of claims 5-17 characterised in that it further comprises one or more selected adjuncts from the group consisting of fluorescent whitening agents, bluing agents, fillers, builders, surfactants, pH adjusters, and mixtures thereof. In an oxidant bleach composition a method for rendering enzymes stable during storage of said bleach composition, said method comprising; encapsulating said enzymes with a soluble coating comprising a protective agent which reacts with and neutralizes enzyme-deactivating oxidant species, said protective agent being: (a) an alkali metal silicate; (b) an alklai metal silicate with an additional additive selected from the group consisting of an antioxidant, a reducing agent or a transition metal; or (c) a water soluble polymer and an additive which is selected from the group consisting of a transition metal or a reducing agent; or (d) a mixture thereof. A process for the preparation of a composition as claimed in claim 1 characterised in the core including the hydrolytic enzyme is coated with the coating layer to encapsulate the core. A process for the preparation of a composition as claimed in claim 5 characterised in that the enzyme granules are made by encapsulating the enzyme core and incorporating them in an oxidant bleach.

Inventors: COYNE THOMAS S, ENGLAND BRUCE J, HAENDLER BLANCA L, JOHNSON CARROLE L, MITCHELL FRANCES E, STEICHEN DALE S, COYNE, THOMAS S., ENGLAND, BRUCE J., HAENDLER, BLANCA L., JOHNSON, CARROLE L., MITCHELL, FRANCES E., STEICHEN, DALE S.
Applicants: CLOROX CO, THE CLOROX COMPANY
Application year: 1988
Main classification: C11D3
IPC codes: C11D7, D06L3, C11D3