Chemical apparatus and process disinfecting – deodorizing – preser – Process disinfecting – preserving – deodorizing – or sterilizing – Maintaining environment nondestructive to metal
Reexamination Certificate
2000-03-31
2003-08-19
McKane, Elizabeth (Department: 1744)
Chemical apparatus and process disinfecting, deodorizing, preser
Process disinfecting, preserving, deodorizing, or sterilizing
Maintaining environment nondestructive to metal
C252S074000, C428S407000, C165S134100, C123S19800E
Reexamination Certificate
active
06607694
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a controlled-release additive composition for use in water treatment systems, particularly coolant and hot water systems, for example, engine coolant systems, and to a method of using said additive compositions. The controlled release additive composition comprises a water-soluble core containing at least one water treatment chemical and a polymeric coating material encapsulating said core which slowly releases the water treatment chemical into the water treatment system, thereby delivering an effective level of the water treatment chemical to the water treatment system over an extended period.
BACKGROUND OF THE INVENTION
Traditionally, additives such as anti-foulants, anti-scaling agents, corrosion inhibitors, buffering and pH agents, microcides and the like are added directly to water treatment systems as needed to prevent scale deposition, corrosion of metal surfaces and similar fouling of water treatment systems, as well to maintain proper pH levels. Typically, a system is monitored, such as by recovering and analyzing a sample, in order to determine the current level of particular chemical treatment agents. When the concentration of a particular agent falls below a desired level, additional agent is added to the system.
Similar methods have been employed for treating coolant systems. For example, the use of conventional antifreeze alone is sometimes insufficient to meet the demands of engine coolant systems. As a result, coolant additives (CA) are added to engine coolant systems to make up for the deficiencies of antifreeze formulations. Typically, coolant additives are added to the engine coolant system at each oil change in order to replace additives which have been diluted or depleted from the system.
Various methods of introducing coolant additives to the engine coolant system have been developed. For instance, a solid CA material may be added directly to the engine coolant system which dissolves in the coolant system. However, this method cannot maintain a steady concentration level of coolant additives within the system. Initially, there would be a high level of the coolant additives released into the system, and within a short time the coolant additives are depleted. Additionally, a significant draw back of this method is the danger of overdosing the system with particular additives which are initially released. The overdosing is dangerous in that it can result in erosion and corrosion problems.
Other attempts to have a good delivery of coolant additives to an engine system include the use of coolant filters which contain coolant additives. These devices operate as bypass filters with coolant flowing through the filter and extracting the coolant additive thereby. Although the use of coolant filters is an improvement over the use of a coolant additive block, the danger of overdosing still exists. For example, recently, there has been an interest in dramatically extending the coolant service interval from the typical two months interval to a once-a-year interval. This in turn increases the interval mileage from 15,000-20,000 miles up to approximately 120,000 miles, or more. Consequently, more additive must be placed into the filter to accommodate the longer time interval. However, the large amount of additive results in a high level of initial release, which is directly related to the creation of certain undesirable side effects to the coolant system, as discussed previously. Furthermore, the use of coolant filters failed to maintain a minimum level of coolant additives within the system.
Minimal attempts have been made in the prior art to address particular water treatment systems by using controlled release coatings. For example, Characklis in U.S. Pat. No. 4,561,981 (issued Dec. 31, 1985) disclosed a method for controlling, preventing or removing fouling deposits, particularly in pipelines, storage tanks and the like by mircroencapsulating fouling control chemicals in a slow release coating. The coating material is described as being any material compatible with the fouling control chemical which is capable of sticking to the fouling deposit site. However, the coating materials as disclosed by Characklis may dissolve in an engine coolant system and create further corrosion problems.
Recently, Mitchell et al. in U.S. Pat. No. 6,010,639 disclosed that a terpolymer may be used as a coating for coolant additives.
However, despite the efforts of the prior art, a need still exists for a controlled release coolant treatment composition.
SUMMARY OF THE INVENTION
Accordingly, the present invention provides a controlled release additive composition for water treatment systems. This invention provides for delayed and more effectively complete release of treatment additive components, to maintain a consistent level of treatment additive components in the water system over an extended period of time. Preferably, the treatment additive components are coolant additive components. Additionally, the water system is preferably a coolant system.
More particularly, the present invention provides a controlled release coolant additive composition for engine coolant systems which slowly releases one or more coolant additive (CA) components into the engine coolant system.
In one embodiment, a controlled release coolant composition has a core containing a water-soluble coolant additive component and a coating substantially surrounding the core.
In a preferred embodiment, the coating is a polymer made up of units from no more than two monomers. More preferably, the units include vinylacetate and vinyl versatate.
The coolant additive component has at least one active ingredient selected from the group consisting of buffering components, captivation liner pitting inhibitors, metal corrosion and hot surface corrosion inhibitors, defoaming agents, hot surface deposition, scale inhibitors, dispersant agents, organic acids, surfactants and mixtures thereof.
In a preferred embodiment, the coolant additive component also includes sodium nitrite, sodium nitrate and sodium molybdate.
In another embodiment, a method is provided for maintaining an effective concentration of at least one engine coolant additive component in an engine coolant system. The method includes steps of circulating the coolant of the system through a filter which contains the controlled release coolant additive composition.
Each and every feature described herein, and each and every combination of two or more of such features, is included within the scope of the present invention provided that the features included in such a combination are not mutually inconsistent.
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to a controlled release coolant additive composition for use in coolant or hot water systems, particularly for use in engine coolant systems. The controlled release coolant additive (CA) composition comprises a core containing a water-soluble coolant additive component and a coating encapsulating said core which enables the slow release of the coolant additive component into the engine coolant system. Any type of coating conventionally known in the art which provides controlled-release properties may be used in the present invention.
In a preferred embodiment, the coating is a polymer dispersion. More preferably, the polymer dispersion has the following properties:
1. Low viscosity: The polymer dispersion should be of a low to medium viscosity. When the viscosity is too high, it would become impossible to pump the polymer dispersion through a coating system. This would cause the line and spray gun to become plugged. Also, in this case, the droplets of polymer dispersion would be too thick and difficult to lose moisture. They would not have the desired level of dryness before they reach the tablet surface. Therefore, the polymer would not form a good and homogeneous coating.
It should be noted that reducing the viscosity of a polymer dispersion through dilution with water is not always a viable solution. Often the dilution leads to changes of
Blakemore Thomas J.
Chen Yu-Sen
Dober Chemical Corp.
McKane Elizabeth
Stout, Uxa Buyan & Mullins, LLP
Uxa Frank J.
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