WO2015038597A1

WO2015038597A1 - Encapsulated oxidizing agent having controlled delayed release

Info

Publication number: WO2015038597A1
Application number: PCT/US2014/054931
Authority: WO
Inventors: Janet AKANDE; Michael J. Unhoch
Original assignee: Arch Chemicals, Inc.
Priority date: 2013-09-10
Filing date: 2014-09-10
Publication date: 2015-03-19

Abstract

Provided is an encapsulated solid oxidizing agent, such as calcium hypochlorite, which is encapsulated with a first coating layer which is predominately a multivalent metal salt or is a thin coating composition of other salts. The multivalent metal salt completely covers the outer surface of the solid oxidizing agent. Additional layers of different coatings may be applied over the first or subsequent layers of coatings. The resulting encapsulated solid oxidizing agents are released from the coating after a period of time in the use environment.

Description

ENCAPSULATED OXIDIZING AGENT HAVING CONTROLLED DELAYED

RELEASE

[0001 ] FIELD OF THE INVENTION

[0002] The present invention relates to an oxidizing agent which is coated or encapsulated with a coating layer. The oxidizing agent is released from the encapsulating coating after a period of time, which introduces the oxidizing agent into the desired use environment.

[0003] BACKGROUND OF THE INVENTION

[0004] In many instances it is desirable to utilize sanitizing or disinfecting agents such as chlorine-based bleach or other non-halogen based oxidizer like sodium percarbonate in the laundry washing process in order to enhance fabric cleaning. There are several different ways to introduce an oxidizing agent into the laundry washing process. The most common way is via the addition of sodium hypochlorite. However, there are several drawbacks associated with using this form of free chlorine in a laundry washing process. For instance, as sodium hypochlorite is limited to a liquid form it tends not to be compatible with a delayed and/or a time release of the chlorine into the wash. Furthermore, this form tends to be incompatible with other common laundry additive materials such as enzymes, polymers, surfactants, color additives such as dyes, brighteners, and fragrance additives as the chlorine will interact with these materials so as to reduce their effectiveness. Yet further, sodium hypochlorite tends to stain and/or remove color if spilled or splashed onto the fabric. Even further, this form of free chlorine at typical addition levels can result in fabric damage over time with repeated usage.

[0005] Calcium hypochlorite is known for its bleaching properties and efforts are on the way to make calcium hypochlorite a product useable in the laundry and other applications. However, calcium hypochlorite is well known to be unstable in the presence of organic materials, such as hydrocarbon fluids, glycerol and the like. One solution to making calcium hypochlorite stable is to coat or encapsulate the calcium hypochlorite with layers of materials. However, these efforts to coat calcium

l hypochlorite have not provided a product with a predictable release profile for the oxidizing agent.

[0006] There is a need in the art for the addition of an oxidizing agent into an automatic clothes washing machine such that the oxidizing agent is released in a predictable manner such that the oxidizing agent is released after the soap detergents and other additives in the detergent have completed their function in the clothes washing process. In addition, there is a need in the art for in other application areas for a timed release of an oxidizing agent, for example, for hygiene purposes, such as toilet bowls, automatic dishwashing machines, recreational water, and industrial water.

[0007] SUMMARY OF THE INVENTION

[0008] In one aspect, the present invention provides an encapsulated oxidizing agent having: a) a core having an outer surface, the core being formed from a composition comprising at least one oxidizing agent; and b) a first coating layer applied to the outer surface of the core, the coating containing as a predominate component of the coating, an alkali metal salt, a multivalent metal salt or hydroxide wherein the coating completely covers the outer surface of the core.

[0009] In a further aspect of the present invention, the encapsulated oxidizing agent is calcium hypochlorite, trichloroisocyanuric acid (TCCA), sodium

dichloroisocyanurate (SDCC), and chloro hydantoins, bromo hydantoins or a mixtures thereof.

[0010] In yet a further aspect of the present invention, the encapsulated oxidizing agent is provide with a second coating layer, the second coating layer being applied over the first coating layer. The second coating layer serves to provide the release profile of the oxidizing agent from the encapsulating coatings. Additional coating layers may be further applied to the second or any subsequent coating layers.

[001 1 ] In a further embodiment of the present invention provided for an

encapsulated oxidizing agent having a core having an outer surface, the core being formed from a composition being at least one oxidizing agent. Covering this core is a first coating layer applied to the outer surface of the core, the first coating layer completely covers the outer surface of the core and the first coating layer has a thickness of 0.5 to 5 microns.

[0012] In a particular embodiment of the present invention, the oxidizing agent is calcium hypochlorite, the first coating layer is predominately calcium hydroxide, and the second coating layer is sodium silicate.

[0013] In a further embodiment of the present invention, the composition is useable as whitening additive for laundry detergents, as a whitening additive for automatic laundry machines, as a toilet bowl cleaner, as sanitizing additive for an automatic dishwashing machine, as a chlorination additive for pools and spas and the like.

[0014] These and other aspects will become apparent when reading the detailed description of the invention.

[0015] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] The present invention provides an encapsulated disinfecting or sanitizing agent, which is coated with one or more layers of one or more coating compositions, where the coating compositions encapsulate the disinfecting or sanitizing agents. In one particular embodiment, the sanitizing or disinfecting agent is an oxidizing agent. It has been surprisingly discovered that the oxidizing agent encapsulated as described herein, can be made to control the release of the oxidizing agent from the encapsulating composition within desired parameters. The resulting encapsulated oxidizing agent has a predictable release profile and releases the oxidizing agent after a period of time when introduced its use environment.

[0017] The oxidizing agent which is encapsulated with the coating composition is generally a solid oxidizing agent. Exemplary oxidizing agents include, for example, calcium hypochlorite or other hypochlorite salts, 1 ,3-dichloro-5,5-dimethylhydantoin (DCDMH), 1 ,3-dibromo-5,5-dimethylhydantoin (DBDMH), 1 -bromo-3-chloro-5,5- dimethylhydantoin (BCDMH), 1 ,3-dichloro-5-ethyl-5-methylhydantoin (DCEMH), 1 ,3- dibromo-5-ethyl-5-methyl hydantoin (DBEMH), 1 -bromo-3-chloro-5-methyl-5- ethylhydantoin (BCEMH), trichlorochlorotriazine (tri-chlor or TCCA),

dichlorochlorotriazine (di-chlor and DCCA) monochlorotriazine (mono-chlor), sodium dichloro-s-triazinetrione dichloride, persalts, for example, persulfates, per carbonates and the like, including for example sodium persulfate and other other chlorine releasing compounds such as glycouril, sulfosuccinates or the like. These oxidizing agents may be in either the anhydrous or hydrated forms. Generally, these oxidizing agents will be in a granular form, having a particle size in the range of about 25 microns to about 2000 microns. The solid oxidizing agents have an outer surface.

[0018] Covering the outer surface of the solid oxidizing agent is a first coating layer. The first coating layer serves to encapsulate the solid oxidizing agent such that the solid oxidizing agent is not exposed once coated with the first coating layer. Suitable first coating layer materials include alkali metal salts and alkaline earth metal salts and hydroxides and other inorganic salts and anhydrides. Of particular interest are sodium chloride and calcium hydroxide as the first layer In one embodiment of the present invention, this first coating layer contains as the predominate component a multivalent metal salt or multivalent metal hydroxide. By the phrase "predominate component" it is intended that the component makes up at least 50 wt% of the first coating layer. Suitable multivalent metals include the alkaline earth metals, e.g. Mg, Ca, and Ba; zinc, copper, aluminum and the like. The term "multivalent" means having a valence greater than or equal to two. Suitable salts include, for example, sulfates, chlorides, phosphates, silicates, and the like. In addition to the salts, hydroxides of these multivalent metals may also be used. One particular example, for the first coating layer is calcium hydroxide.

[0019] Generally, the first coating layer will have be at least 60 wt% of the multivalent alkali metal salt or metal salt or hydroxide, and typically at least 80 wt%. The weight percentage is of the dried coating on the oxidizing agent.

[0020] The first coating layer is applied on the solid oxidizing agents in any know manner, including spray dried coating processes. It has been discovered that the multivalent metal salts or hydroxides provide an improved release profile that is easier to control than monovalent metal salts or monovalent metal hydroxides.

Further, the multivalent metal salts and/or hydroxides tend to convert the oxidizing agent to an anhydrous form, making the oxidizing agent more stable. This is especially true for the oxidizing agent calcium hypochlorite. Improved stability is important when handling extremely reactive compounds such as calcium

hypochlorite. [0021 ] The first coating layer is applied to a thickness of the coating in the range of about 0.5 to about 5 microns in thickness. Typically the first coating layer will be in the range of about 1 to about 3 microns. It has been discovered that thicker layers of the first coating layer provides minimal increase in stability or release profile. It has also been discovered that the first coating layer is sufficient to keep the oxidizing agent from reacting with material outside of the first coating layer. That is, when the oxidizing agent is calcium hypochlorite, the first coating layer will protect the calcium hypochlorite from organic materials, such as hydrocarbons, glycerol and the like, which come into contact with the first coating layer.

[0022] In addition to the first coating, additional coatings may be applied over the first coating layer. The additional coating layers serve to control the release profile of the oxidizing agent from the encapsulating layer. Generally, the second or additional layers applied to the first coating layer will be a material that is water soluble. As the second or subsequent layer dissolve in water of the use environment, the water will contact the first layer, dissolving the first coating layer, thereby releasing the oxidizing agent form the encapsulating materials. The second or subsequent layers can be prepared from a wide variety of materials, including organic materials, such as polyvinylalcohol, polyacrylic acid, polyvinylacetate, and other similar water soluble organic materials. Alternatively, the second or any additional coating layers maybe soluble inorganic materials. Soluble inorganic materials suitable for the

encapsulating the encapsulate of the invention include alkali materials such as sodium bicarbonate, sodium sesquicarbonate, sodium borate, potassium

bicarbonate, potassium sesquicarbonate, potassium borate, phosphates such as diammonium phosphate, monocalcium phosphate, monohydrate, tricalcium phosphate, calcium pyrophosphate, iron pyrophosphate, magnesium phosphate, monopotassium orthophosphate, potassium pyrophosphate, disodium

orthophosphate dihydrate, trisodium orthophosphate decahydrate, tetrasodium pyrophosphate, sodium tripolyphosphate, a sodium polyphosphate compound, sodium hexametaphosphate, potassium tripolyphosphate, a potassium

polyphosphate compound, neutral or soluble salts such as sodium sulfate, sodium chloride, silicates, such as sodium or potassium silicates, tetrasodium or

tetrapotassium pyrophosphate, pentasodium or pentapotassium tripolyphosphate, hydrated or anhydrous borax, sodium or potassium sesquicarbonate, phytates, polyphosphonates and other similar materials. Of particular interest are silicates, in particular sodium silicate.

[0023] Generally, the release of the oxidizing agent from the encapsulating layer can be controlled by the selection of the second and subsequent encapsulating layer and the thickness of the second and subsequent encapsulating layers. The thicker the second or subsequent encapuslating layers the longer it takes for the oxidizing agent to be released from the encapsulating coating. In the present invention, the second or subsequent encapulslating layer can be up to about 10 microns thick, or thicker depending on the desired release profile. An exemplary thickness for the second and subsequent coating is general in the range of 0.1 -5 microns. Typically, for shorter release times, the second or subsequent coats of the coating composition are in the range of 0.25-2 microns. It was also unexpectedly discovered that thinner encapsulating layers result in a more stable oxidizer as compared can be achieved by thicker coatings. Stability here is intended to mean heat stability above about 140°F (60°C).

[0024] The manufacture of the encapsulated oxidizing agent can be carried out by first providing an initial inorganic protective passivation coating of the core material which can be conveniently applied using fluidized coating apparatus. In making encapsulated materials, the particulates are introduced into the fluidizing chamber of a fluidized bed. The bed of particles to be coated is then suspended with the fluidizing atmosphere. A nozzle is typically introduced into or nearby the fluidized bed through which liquid droplets of coating material are discharged in a diverging pattern coextensive with the upper surface of the bed. Coating solution is applied to the bed at a temperature required for rapid drying of the coating solution on the core particles. Solvent vapors can be removed from the fluidized bed with a blower.

[0025] A encapsulated oxidizing agent in the present invention is typically produced by a spray fluid bed coater such as Mini-Glatt and GPCG-1 from Glatt Air Technologies, Inc., and ACT 100N and ACT 300N from Applied Chemical

Technology, Inc. In the case of calcium hypochlorite, the variables and conditions of coating are specifically controlled to have minimum wetting on the surface of the oxidizing agent particles, and generate suitable mixtures with hydrated salts. A multiple layer coating is accomplished by sequential feeding of deemed coating materials under suitable coating conditions. Coating may be conducted using either a batch or continuous process. Additionally, according to the present invention, a continuous feeding of aqueous coating solution is used to produce a controlled homogenous or heterogeneous single or multilayer coated granular calcium hypochlorite composition.

[0026] The present invention is further described in detail by means of the following Examples. All parts and percentages are by weight and all temperatures are degrees Celsius unless explicitly stated otherwise.

[0027] EXAMPLES

[0028] An 100 N fluidized bed spray coater was used to prepare the sample shown in Table 1 . The coated calcium hypochlorite in the following examples shown in Table 1 were produced by an ACT 100N spray fluid bed coater from Applied Chemical Technology, Inc. at inlet air temperature of 50-75° C and product temperatures of 35-55° C. A multiple layer coating was accomplished by sequential feeding of coating materials under the conditions at the same or different inlet and product temperatures. The pump rate of a coating solution was specifically controlled to achieve suitable particle wetting and drying to minimize loss of available chlorine. Typically, the pump rate was set to 10ml/min. As is known in the art, although these examples were made using a batch process, other processes, such as continuous processes, may also be employed for production of these materials.

[0029] TABLE 1

of 200 ml with Dl

water

3 Calcium Sodium 95.5 g 45 g of NaCI 5.0%

Hypochlorite chloride dissolved in Dl

water to a volume

of 500ml

4 Sample 3 Sodium 400 g 5.4 g of a 37% 0.5%

Silicate Na₂Si03 solution

diluted to a volume

of 200 ml with Dl

water

[0030] The encapsulated oxidizing agent of the present invention may be used in any use that requires the use of an oxidizing agent, where delayed release of the oxidizing agent is desirable. Exemplary uses include as whitening additive for laundry detergents, as a whitening additive for automatic laundry machines, as a toilet bowl cleaner, as sanitizing additive for an automatic dishwashing machine, as a sanitizing or disinfecting additive for pools and spas and the like.

[0031 ] While the invention has been described above with references to specific embodiments thereof, it is apparent that many changes, modifications and variations can be made without departing from the invention concept disclosed herein.

Accordingly, it is intended to embrace all such changes, modifications, and variations that fall within the spirit and broad scope of the appended claims.

Claims

What is claimed is:

1 . An encapsulated oxidizing agent comprising

a) a core having an outer surface, the core being formed from a composition comprising at least one oxidizing agent ; and

b) a first coating layer applied to the outer surface of the core, the coating containing as a predominate component of the coating, an alkali metal salt, a multivalent metal salt or hydroxide wherein the coating completely covers the outer surface of the core.

2. The encapsulated oxidizing agent according to claim 1 , wherein the oxidizing agent is selected from the group consisting of calcium hypochlorite,

trichloroisocyanuric acid (TCCA), sodium dichloroisocyanurate (SDCC), and chloro hydantoins, bromo hydantoins and mixtures thereof.

3. The encapsulated oxidizing agent according to claim 1 , wherein the multivalent metal of the metal salt or metal hydroxide comprises an alkaline earth metal, aluminium, copper or zinc.

4. The encapsulated oxidizing agent according to claim 1 wherein the alkali metal salt is sodium chloride or sodium silicate.

5. The encapsulated oxidizing agent according to claim 3, wherein the multivalent metal hydroxide is calcium hydroxide.

6. The encapsulated oxidizing agent according to claim 1 , wherein the first coating layer has a thickness of 0.5 to 5 microns.

7. The encapsulated oxidizing agent according to claim 6, wherein the first coating layer has a thickness of 1 -3 microns.

8. The encapsulated oxidizing agent according to claim 1 , further comprising a second coating layer, the second coating layer being applied over the first coating.

9. The encapsulated oxidizing agent according to claim 8, wherein the second coating layer comprises sodium silicate.

10. The encapsulated oxidizing agent according to claim 8, wherein the second coating is an organic coating.

1 1 . The encapsulated oxidizing agent according to claim 8, wherein the organic coating comprise polyvinyl alcohol.

12. The encapsulated oxidizing agent according to claim 8, wherein the second coating layer has a thickness of about 0.25 to about 2.0 microns.

13. The encapsulated oxidizing agent according to claim 1 , wherein the oxidizing agent comprises calcium hypochlorite, the first coating layer comprises calcium hydroxide.

14. The encapsulated oxidizing agent according to claim 13, wherein the first coating layer has a thickness of 1 -3 microns.

15. The encapsulated oxidizing agent according to claim 13, further comprising a second coating, the second coating being applied over the first coating.

16. The encapsulated oxidizing agent according to claim 15, wherein the second coating comprises sodium silicate.

17. The encapsulated oxidizing agent according to claim 16, wherein the second coating layer has a thickness of about 0.25 to about 2.0 microns.

18. An encapsulated oxidizing agent comprising

b) a first coating layer applied to the outer surface of the core, the coating completely covers the outer surface of the core and has a thickness of first coating layer has a thickness of 0.5 to 5 microns.

19. The encapsulated oxidizing agent according to claim 18, further comprising a second coating layer, the second coating layer being applied over the first coating layer.

20. The encapsulated oxidizing agent according to claim 19, wherein the second coating layer has a thickness of about 0.25 to about 2.0 microns.

21 . A detergent composition comprising the encapsulated oxidizing agent of any one of the proceeding claims.

22. A laundry bleaching composition comprising the encapsulated oxidizing agent of any one of claims 1 -20.

23. A toilet bowl cleaner comprising the encapsulated oxidizing agent of any one of claims 1 -20.

24. An automatic dishwashing composition comprising the encapsulated oxidizing agent of any one of claims 1 -20.