AN ENCAPSULATED HYPOCHLORITE DEACTIVATOR

Abstract: A denture cleansing composition of the hypochlorite type is rendered substantially free of hypochlorite chlorine odour by incorporating into the composition a hypochlorite deactivator. The deactivator is released into the cleansing solution at a controlled rate to optimize cleansing efficacy at a reduced hypochlorite chlorine odour. The deactivators suit­ able for use in this invention include sodium perborate mono­ hydrate and sodium nitrite. The preferred method of controlling deactivator release rate is by encapsulating the deactivator.

Description: This invention relates to a denture cleansing composition comprising a hypochlorite generating agent and a hypochlorite deactivator which is substantially free of chlorine odor. More particularly it relates to a hypochlorite type denture cleansing composition having incorporated therein a controlled release deactivator for the hypochlorite. Effervescent denture cleansers have been long known in the art. Most of those presently on the market derive their cleansing efficiency mainly from peroxy compounds which provide active oxygen. While the active oxygen provides a good bleaching action, it has relatively poor plaque removing properties. Various peroxygen type denture cleansers are described in U.S. Patent Nos. 2,498,343; 2,498,344; 2,931,776 and 3,243,377. Another type of denture cleanser described in U.S. Patent No. 3,113,111 derives its cleansing efficacy from an active chloride source and has good plaque removing properties. The product, however, is not effervescent and must be stirred mechanically to dissolve. An effervescent denture cleansing composition which releases hypochlorite/chlorine on contact with water is disclosed in U.S. Patent No. 3,936,385. The product has good plaque removing properties and dissolves without stirring. However, it is not fully acceptable because of the chlorine odor associated with the product and its tendancy to corrode metals. Efforts to mask odor using fragrances have been unsuccessful because of the strong hypochlorite odor. Recent improvements in these hypochlorite type of denture cleansing composition include the disclosure of U.S. Patent No. 4,362,639 to Eoga. The denture cleanser of that disclosure include ammonium ion compounds which inhibit hypochlorite odor emission and inhibit metal tarnish or corrosion. However, amine compounds may result in the generation of undesirable chloramines. The art is replete with references which teach the reaction of hypochlorite solutions with a wide range of compounds. An article entitled "Kinetic Studies on the Chloramines," authored by Ira Weil and J. Carrell Morris, J . Am . Chem . Soc , 71 , 1644-1671 (1949) discloses reactions of ammonia and primary amines with hypochlorite. The reaction of hydrogen peroxide and hypochlorous acid has been studied; see for example "The Interaction of Hydrogen Peroxide and Hypochlorous Acid in Acidic Solutions Containing Chloride Ion" Connick, R.R., J . Am . Chem . Soc , 69 , 1509-1514 (1947). Similarly the reactions of iodates and nitrites are taught in the art; see "The Oxidation of Nitrite and Iodate Ions by Hypochlorite Ions," Lister, M. W. and Rosenblum, P., Canadian Journal of Chemistry , 39 , 1645-1651 (1961). Hydrazine dihydrochloride has been taught as a chlorine scavanger. See "Chlorine Scavenger for HCL Gas Streams" page 539 Merck Index 8th Ed., 1968. Guanidine has also been used to scavenge chloride in sewer gases. U.S Patent No. 4,295,985 discloses a soap which removes chlorine odor from the skin and hair of bathers. The composition is said to neutralize chlorine (as hypochlorite). Compounds taught to be suitable neutralizing agents are sodium nitrite, sodium sulfite, sodium thiosulfate, urea, thiourea, ascorbic acid, hydrazine, hydroxylamine, pyrrole, sodium ferrocyanide, hydroquinone, formaldehyde, furfural, sodium hypophosphate and sodium hydrosulfite. In general, the prior art approach has been to add the deodorizing agent to the denture cleansing composition. As such, it immediately begins to reduce the available hypochlorite. Hence, either reduced efficiency must be accepted or substantially larger amounts of cleansing agent, at increased costs, must be utilized to achieve the desired effect. Various methods are taught in the art for delaying the activity of a particular component of the denture cleansing composition. For example, U.S. Patent No. 3,952,107 discloses a two part tablet which preferentially releases an enzyme to attack the proteinaceous materials which are loosely bonded to plaque. Subsequently, an oxygen generating agent is released to complete the cleaning. The delay time between each activation step is disclosed to be about 60 to 120 seconds. The time release is accomplished by consideration of the relative thickness of the two layers, the proportion of the effervescent producing composition in each layer and the particle size of certain ingredients in each layer. Similarly, U.S. Patent No. 4,256,999, discloses a two layer denture cleansing tablet, each of which disintegrate at controlled rates to give improved cleaning efficiency. Various techniques, including the use of silicic acid and polyvinyl pyrrolidone, to control the release rate are taught. In FR-A-2256767, there is disclosed a two component capsule which is prepared by encapsulating sodium thiosulphate in a layer of hydroxyethyl methacrylate/ethylene glycol methacrylate copolymer, and by then forming an outer layer of lithium hypochlorite and KH₂PO₄-Na₂HPO₄. When the capsule is placed in water, the sodium hypochlorite dissolves to form a solution suitable for sterilizing a hydrophilic contact lens. There is no teaching in the art of a method for preparing a substantially odour free, hypochlorite releasing denture cleanser. It has surprisingly been found that a hypochlorite generating type denture cleansing composition can be rendered free of objectionable hypochlorite derived odour without loss of cleansing efficiency by incorporating into the composition a hypochlorite deactivator, the activation of which is controlled to minimize any deleterious effect on cleansing. Controlled release of the deactivator compound is accomplished either by incorporating it into a two part tablet (as in disclosed in our European Patent Application No. 891193399.7 (EP-A-0360299)) or by encapsulating the deactivator to form controlled released microcapsules (as is disclosed in the present application). Thus according to the present invention, there is provided a controlled release encapsulated hypochlorite deactivator composition comprising: (a) hypochlorite deactivator beads or granules comprising alkali metal nitrite or alkali metal perborate and having a particle size of about 297 to about 841 micrometres (about 20 to about 50 U.S. standard stainless steel mesh), and (b) a coating composition completely surrounding and enclosing said deactivator beads or granules, the coating composition comprising (i) a water-insoluble pH-insensitive film-forming composition, said film-forming composition being permeable to water, nitrite ions and perborate ions at a pH of about 8.5 to about 11, and (ii) a plasticizer in an amount of from about 18 to about 40% by solid weight of said film-forming composition; wherein the coating composition comprises about 6% to about 20% (w/w) of the encapsulated deactivator composition. The present invention also provides a denture cleansing composition comprising (i) a hypochlorite generating agent and (ii) a controlled release encapsulated hypochlorite deactivator composition of the invention. The present invention also provides a process for preparing a controlled release hypochlorite deactivator composition, which comprises: contacting hypochlorite deactivator beads or granules comprising alkali metal nitrite or alkali metal perborate and having a particle size of about 297 to about 841 micrometres (about 20 to about 50 U.S. standard stainless steel mesh) with a coating composition to encapsulate the hypochlorite deactivator beads or granules, the coating composition comprising (i) a water-insoluble pH-insensitive film-forming composition, said film-forming composition being permeable to water, nitrite ions and perborate ions at a pH of about 8.5 to about 11, and (iii) a plasticizer, wherein the coating composition is present in an amount of from 6% to 20% by weight based on the total weight of the encapsulated beads or granules, and wherein the plasticizer is present in an amount of from 18% to 40% by weight based on the solid weight of the film-forming composition; and curing the encapsulated deactivator beads or granules for 45 minutes to 75 minutes at a temperature of from 85°C to 100°C. The present invention also provides an effervescent denture cleansing composition which comprises: an effervescent first part having incorporated therein a cleansing agent comprising a hypochlorite generating agent; and an effervescent second part having incorporated therein a hypochlorite deactivator; wherein the hypochlorite deactivator is a controlled release encapsulated hypochlorite deactivator composition of the invention. Reference is made hereinbelow to the drawing, the single Figure of which is a graph of hypochlorite elimination by deactivator as a function of time. The invention relates to a hypochlorite generating type of denture cleansing agent. More particularly it relates to an effervescent denture cleanser which utilizes a hypochlorite generating compound as a plaque removal agent. Specifically it relates to a method for rendering the hypochlorite cleansing composition free of objectional odor without loss of efficiency of the cleansing agent. This end is accomplished by incorporating into the denture cleansing composition a hypochlorite deactivator which is activated by controlled release over the cleansing cycle. As used in the specification and claims the term "denture" means all those removable orthodontic appliances such as false teeth, dental plates and bridges. In the practice of this invention any alkali metal nitrite or perborate can be used as a hypochlorite deactivator, to react with a hypochlorite in solution to neutralize hypochlorite/chlorine odor. The preferred alkali metals are sodium and potassium. Illustrative examples of suitable hypochlorite deactivators are sodium nitrite, potassium nitrite and sodium perborate monohydrate. As used in the specification and claims, the term "hypochlorite generating agent" means any compound which upon contact with water generates or releases hypochlorite ion directly or by the interaction of two or more compounds. Illustrative, non-limiting examples of the hypochlorite generating agent of this invention are heterocyclic N-chloroimides such as a chloroisocyanurate, e.g., sodium dichloroisocyanurate, potassium dichloroisocyanurate, or trichlorocyanuric acid; complex salts of two or more compounds, e.g., [(mono-trichloro)-tetra-(monopotassiumdichloro)]penta-isocyanurate; other N-chloroimides, e.g., sodium p-toluene-sulfonochloramide, N,Ndichloro-p-toluenesulfonamide, sodium benzene-sulfonchloramide, N,N-dichlorobenzene-sulfonamide, N-chlorosuccinate. Still other compounds which liberate hypochlorite/chlorine on contact with water are N-chloro malonimide, N-chloro phthalinide and N-chloro naphthalimide; the hydantoins such as 1,3-dichloro-5,5-dimethyl hydrantoin; N-monochloro-C,C-dimethylhydrantoin; methylene-bis-(N-chloro-C,C-dimethylhydantoin); 1,3-dichloro-5-ethylhydantoin and 1,3-dichloro-5,5-diisoethylhydantoin; dry solid inorganic compound such as lithium hypochlorite, calcium hypochlorite; mixtures of salts, such as sodium persulfate and sodium chloride; sodium perborate and chlorinated 5-triazine triones. In order to utilize the hypochlorite deactivator without adversely effecting the effectiveness of the hypochlorite as a cleansing agent it is necessary to delay the action of the deactivator until the cleansing action is complete. Otherwise, the deactivator will be destroying hypochlorite which is necessary for cleansing the denture. Generally, the cleansing action is complete in about 8 to about 20 minutes; and preferably about 10 to about 18 minutes. The action of the hypochlorite deactivator is controlled in that the hypochlorite deactivator is encapsulated into microcapsules which are formulated to control the release of the deactivator over the cleansing cycle. Thus the hypochlorite deactivator is encapsulated in a film forming material which will control the rate of release at a rate which does not adversely affect the cleansing action of the hypochlorite. Ideally, no deactivator will be made available until the entire cleansing cycle is complete. It will be appreciated by those skilled in the art that in the time frame of the denture cleansing cycle, about 8 to about 20 minutes, it is not possible to accomplish that end. Hence, the ideal must be approximated by controlling the rate of release of deactivator so as not to consume so much hypochlorite as to adversely affect the cleansing action. This concept will be more readily appreciated by reference to the Figure. Referring now to the Figure curve "a" represents the idealized hypochlorite concentration curve over a denture cleansing cycle t. The hypochlorite instantaneously reaches its maximum value and is immediately eliminated at the end of the cleansing cycle by the subsequent release of deactivator. Prior art methods of including a hypochlorite deactivator in the denture cleansing composition result in a hypochlorite concentration curve represented by curve "b." The hypochlorite is maintained at a low level throughout the cleansing cycle. Hence, cleansing efficiency is greatly reduced. Curve "c" represents the results achieved by the method of this invention where k is the available hypochlorite concentration at end of the cleaning cycle. Ideally, k is zero. However, time and economic constraints require that k be fixed at same acceptable level which will permit hypochlorite derived odor to be masked by an acceptable fragrance. It is necessary that not only the odor of the solution, but the odor produced upon the reaction of hypochlorite ion with the proteinaceous material, e.g., the skin of the fingers and hand, be eliminated. It is this latter odor which is of primary concern since the solution odor is only mildly objectionable. The term "hypochlorite derived odor" as used in the specification and claims means solution odor as well as odor resulting from the attack of hypochlorite on proteinaceous material. The value of "k" is not itself significant since the test of an acceptable odor is a subjective one which must be determined by correlating product parameters with the perceived results as evaluated by users of the product. Any of the commercially available spray dried fragrances are suitable for the practice of this invention. The spray dried fragrances comprise a fragrance oil which has been deposited on a solid, such as maltodextrin, by a solution spray drying technique. Illustrative, non-limiting examples of spray dried fragrances which can be used in the practice of this invention are peppermint, wintergreen, lime, lemon, menthol, and so forth. While the amount of fragrance used is a matter of choice at least 0.1% (w/w) based on the total denture cleansing composition should be used in order to mask the hypochlorite-chlorine odor. The hypochlorite deactivator is encapsulated in a barrier film which controls the rate of dissolution of the hypochlorite deactivator in the denture cleaning solution. While the encapsulation technique used in the practice of this invention is well known in the art, there are certain parameters which are critical to the successful encapsulation of a hypochlorite deactivator which is effective for the purpose of this invention. These parameters include selection of the coating material, particle size of the hypochlorite deactivator, weight percent of coating material relative to deactivator weight, the method of application of coating material and the amount of plasticizer used in the encapsulating film. The hypochlorite deactivator is utilized in either bead or granule form, and has a particle size of less than 20 mesh to about 50 mesh (U.S. standard stainless steel mesh). The appropriate particle size may be selected by sieving the deactivator and rejecting material which is collected on a 20 mesh screen and which passes through a 60 mesh screen. Particles larger than about 20 mesh cannot be used since they create problems in the feeder and hopper of the tabletting machine, e.g., segregation. At a particle size substantially smaller than 50 mesh the particles have too large a surface area and encapsulation become uneconomical because of the large quantities of encapsulating material required. The encapsulating material must be used at about 6% to about 20% by weight based on the total weight of the encapsulated deactivator particle, preferably about 12% to about 20%, and more preferably about 14% to about 20%. At less than 6% by weight of coating of encapsulating material the deactivator dissolves too quickly in the hypochlorite denture cleanser solution resulting in insufficient hypochlorite being available for cleaning. At above about 20% by weight of the coating of encapsulating material the dissolution rate is too slow to be of any value from a practical cleaning cycle standpoint. The coating can be applied either from a solution or an emulsion. In applying the coating during the encapsulation process, the solids content of the vehicle should be about 6 to about 30% (w/w) based on the total weight of vehicle plus coating. Below 6% solids inordinately long times are required to apply the coating. At high solids content, i.e. greater than 30% (w/w), the solution or emulsion was either too viscous or the coatings were not uniform. A plasticizer is required for the coating to ensure good film-forming characteristics. Excessive amounts of plasticizer results in stickiness and agglomeration of coated particles. Too low a level results in a discontinuous coating and as a consequence immediate dissolution of deactivator. Thus, about 18% to about 40% (w/w) based on the film former solids is used, preferably about 20% to about 30% (w/w). It should be noted that reference to coating weight includes film former, plasticizers and adjunctives which may be included in the coating formulation. The type of plasticizer used will depend on the selection of film former. Specific plasticizers are normally recommended by the film former supplier and no advantage is seen in deviating from these recommendations. Where the film former is ethyl cellulose the recommended plasticizer is dibutyl sebacate. Triethyl citrate can also be used. The film former must not be water soluble. Since the pH of denture cleansing solutions is about 8.5 to 11.0, e.g. 9.0 to 10.0, the film former must not be solubilized by basic solutions. Hence, the enteric coatings normally used for drugs are ineffective. The film former must, therefore, be water insoluble. Furthermore, it must either be permeable with respect to H₂O and nitrite ions, or adjunctives which are water soluble or hydrophilic must be included in the film. The latter technique is well known in the art. For example, water soluble polymers such as polyvinyl alcohol can be incorporated into the coating at about 2% to about 10% by weight. Alternatively, the adjunctive can be a water insoluble material rendered soluble at high pH, e.g. polyvinyl acetate phthalate (PVAP) or butyrate (PVAB). The film former is preferably swelled by water. PVAB and PVAP may be utilized as the film former at coating weights of about 25 to about 30% (w/w). The preferred film former is ethyl cellulose. Other film formers which may be utilized either directly or with the aid of adjunctives are styrene-maleic anhydride copolymers and sulfonated polystyrene wherein the sulfonation comprises less than 15 mole % of the polymer e.g. 5-10 mole %. Other sulfonated polymers such as sulfonated ethylene-propylene-terpolymers (EPDM), with the same caveat as to degree of sulfonatin, and polyvinyl acrylate may be used. The method of encapsulation is well known to those skilled in the art and can be accomplished with known techniques. Those skilled in the art will recognize that the objective is to produce a dry, non-tacky coated product, and therefore, will appreciate what process parameters are required to achieve that end. The film former is preferably applied by spraying a solution or emulsion into the air inlet stream of a fluidized bed comprising the particles to be coated. To ensure evaporation of the vehicle the inlet air temperature should be about room temperature 23°C, to about 65°C. Sufficient air flow is required to fluidize the particles so that a "boiling bed" condition exists. The air flow rate will depend on the bed height (charge) and particle density. As those skilled in the fluidization art will recognize, the flow rate must be sufficient so that the pressure drop through the bed exceeds the bed weight per unit area. However, excessive flow rates are to be avoided to minimize attrition or fracture of particles. An air flow rate of about 30 to about 80 m³/hr has been found to be adequate, preferably the air flow rate is about 55 to about 75 m³/hr. It has been found that in order for the coated particles to be compressible without damage it is necessary to cure the coated particles at about 85°C to 100°C for about 45 minutes to about 75 minutes, preferably about 90°C for about 55 to 65 minutes. Lower temperatures are ineffective and higher temperatures adversely affect the film stability. As used in the specification and claims the term "coating medium" means the film former, plasticizers and adjunctives in a solvent or as an emulsion. The encapsulation process of this invention is illustrated by the following examples. EXAMPLE I Coating of NaNO ₂ Particles of NaNO₂ in the 20 to 50 mesh range were coated with a plasticized film of ethyl cellulose. The air inlet temperature was room temperature and the carrier air flow rate was 55/m³/hr. The coating medium was introduced to the unit at 5 ml/min. The product was dried in the column for about 15 min. at 65°C and subsequently cured at about 90-95°C for one hour. The coating weight was 8% (w/w) based on the NaNo₂. The coating medium had the following formulation: Coating Solution w/w % Ethyl Cellulose 5.0 Dibutyl Sebacate 1.0 Stearyl dimethyl benzyl NH₄Cl 0.25 Ethanol 93.75 Approximately 0.400 Kg of material was coated using about 0.65 Kg of solution. EXAMPLE II The method of Example I was repeated using 0.200 Kg of NaNO₂. The inlet air temperature was 60°C and the fluidizing air flow rate was 75 m³/hr. Instead of an alcohol solution the coating was applied from an emulsion which included an ethyl cellulose latex emulsion (30% solids). The formulation of the coating medium was as follows: Component w/w % Ethyl Cellulose latex emulsion 50.00 Dibutyl Sebacate 3.00 Deionized Water 46.965 Talc 0.035 The finished product comprised a coating of 15.25% (w/w) based on the NaNO₂. The product was oven dried for 1 hour at 90°C. EXAMPLE III Example I was repeated using 0.400 Kg of sodium perborate, monohydrate. The fluidizing air flow rate was 32 m³/hr and the spray rate was 8 ml/min sustained for 65 minutes. The formulation of the coating medium was as follows: Component w/w% Ethyl Cellulose 5.0 Dibutyl Sebacate 1.0 Ethanol, Anhydrous 94.0 EXAMPLE IV Tablets were prepared using the compositions shown in the Table incorporating sodium dichloroisocyanate as the hypochlorite generating agent and the deactivators of Examples I, II and III. The amount of deactivator used is the stoichiometric amount with respect to the amount of dichloroisocyanurate. TABLET COMPOSITION A mg/tab B mg/tab C mg/tab Sodium Bicarbonate 285 285 285 Sodium Sulfate 90 90 90 Citric Acid 190 190 190 Sodium Carbonate 1450 1450 1450 Ethylenediaminetetraacetic Acid, Na₄.salt 60 60 60 Sodium Dichloroisocyanurate 560 560 560 Sodium Perborate Monohydrate 240 240 240 Detergent 15 15 15 Magnesium Stearate 10 10 10 Coated Na Perborate H₂0 (Example III) 270 - - Coated NaNO₂ ("A") (Example I) 380.43 - Coated NaNO₂ ("B") (Example II) - - 413.12 The best overall results were achieved with the NaNO₂ having a coating weight of 15.28% (w/w). EXAMPLE V Example II was repeated and encapsulated NaNO₂ having coating weights (% w/w) of 6, 8, 10, 12, 14, 16, and 20%. Tablets were prepared using the formulation of Run C of the Table of Example IV. The total weight of encapsulated deactivator was adjusted to compensate for coating weight thereby ensuring that a stoichiometric amount of deactivator was present. The effectiveness of each of the compositions was evaluated by testing the odor characteristics and cleansing efficacy of each. Tests subjects were asked to evaluate the objectionability of hypochlorite derived odor from the solution and on the skin. All of the compositions were acceptable from the standpoint of hypochlorite derived odor. Cleansing efficacy was found to be marginal below 12 weight percent of coating. Optimum results were achieved at a coating weight of 18%. At 20% there was no substantial improvement in cleaning over the 18% coating which would not justify the increased cost of coating. It was found that from the standpoint of cleansing efficacy and solution odor the optimum results were achieved with the 18% (w/w) coating. While lighter coatings resulted in reduced odor they also resulted in poorer cleaning. At 18% (w/w) coating the odor was sufficiently reduced to be masked by a spray-dried peppermint fragrance. The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit of scope of the invention and all such modifications are intended to be included within the scope of the claims.

Claims: A controlled release encapsulated hypochlorite deactivator composition comprising: (a) hypochlorite deactivator beads or granules comprising alkali metal nitrite or alkali metal perborate and having a particle size of about 297 to about 841 micrometres (about 20 to about 50 U.S. standard stainless steel mesh), and (b) a coating composition completely surrounding and enclosing said deactivator beads or granules, the coating composition comprising (i) a water-insoluble pH-insensitive film-forming composition, said film-forming composition being permeable to water, nitrite ions and perborate ions at a pH of about 8.5 to about 11, and (ii) a plasticizer in an amount of from about 18 to about 40% by solid weight of said film-forming composition; wherein the coating composition comprises about 6% to about 20% (w/w) of the encapsulated deactivator composition. A composition according to claim 1, wherein the film-forming composition is ethyl cellulose, and the plasticizer is dibutyl sebacate. A composition according to claim 1 or 2, wherein the coating composition is present in an amount of from 14% to 20%, preferably 16% to 20%, more preferably approximately 18%, by weight based on the total weight of the encapsulated deactivator. A composition according to any of claims 1 to 3, wherein the alkali metal is sodium. A composition according to claim 4, wherein the deactivator is NaNO₂. A denture cleansing composition comprising (i) a hypochlorite generating agent and (ii) a controlled release encapsulated hypochlorite deactivator composition as claimed in any of claims 1 to 5. A composition according to claim 6, wherein the deactivator composition is present in an approximately stoichiometric amount based on the amount of the hypochlorite generating agent. A process for preparing a controlled release hypochlorite deactivator composition, which comprises: contacting hypochlorite deactivator beads or granules comprising alkali metal nitrite or alkali metal perborate and having a particle size of about 297 to about 841 micrometres (about 20 to about 50 U.S. standard stainless steel mesh) with a coating composition to encapsulate the hypochlorite deactivator beads or granules, the coating composition comprising (i) a water-insoluble pH-insensitive film-forming composition, said film-forming composition being permeable to water, nitrite ions and perborate ions at a pH of about 8.5 to about 11, and (iii) a plasticizer, wherein the coating composition is present in an amount of from 6% to 20% by weight based on the total weight of the encapsulated beads or granules, and wherein the plasticizer is present in an amount of from 18% to 40% by weight based on the solid weight of the film-forming composition; and curing the encapsulated deactivator beads or granules for 45 minutes to 75 minutes at a temperature of from 85°C to 100°C. A process according to claim 8, wherein the plasticizer is present in an amount of from 20% to 30% by weight based on the solid weight of film-forming composition. A process according to claim 8 or 9, wherein the coating composition is applied by a fluidised-bed spray-coating process from a solution or an emulsion of the coating composition. A process according to claim 10, wherein the coating composition is present in an amount of from 6% to 30% by weight of the solution or emulsion. A process according to claim 11, wherein the coating emulsion comprises: approximately 50% by weight of an ethylcellulose emulsion which has a solids content of about 30% by weight; and dibutyl sebacate in an amount of approximately 3% by weight based on the weight of the coating emulsion. An effervescent denture cleansing composition which comprises: an effervescent first part having incorporated therein a cleansing agent comprising a hypochlorite generating agent; and an effervescent second part having incorporated therein a hypochlorite deactivator; wherein the hypochlorite deactivator is a controlled release hypochlorite deactivator composition according to any one of claims 1 to 5. A composition according to claim 13, wherein the hypochlorite generating agent is sodium dichloroisocyanurate. A composition according to claim 13 or 14, wherein the hypochlorite deactivator is sodium perborate or sodium nitrite, preferably sodium nitrite. A composition according to any one of claims 13 to 15, wherein the second part disintegrates in water at a slower rate than the first part. A composition according to claim 16, wherein the second part has a controlled rate of disintegration, the rate being controlled by incorporating therein a predetermined quantity of an effervescent agent. A composition according to claim 17, wherein the effervescent agent is a mixture of an alkali metal bicarbonate, preferably sodium bicarbonate, and a water soluble organic acid, preferably citric acid, the mixture being present in an amount of from 20% to 40% by weight based on the total weight of the second part, or by weight based on the total weight of the tablet. A composition according to claim 18, wherein the effervescent agent is an alkali metal perborate monohydrate, preferably sodium perborate monohydrate, present in an amount of from 15% to 20% by weight based on the total weight of the second part, or by weight based on the total weight of the tablet.

Inventors: SCHOBEL, ALEXANDER M., SCHUMACHER, ROBERT W.
Applicants: WARNER-LAMBERT COMPANY
Application year: 1984
Main classification: A61L2
IPC codes: C11D17, A61L2, C11D7, A01N59, A61K8, A61Q11