Patent Application
20070270524
Essentially the instant invention proposes a unique process for coating aggregates using the industry standard process producing a coated aggregate with standard properties for use in casting industry and as a proppant in the oil industry while offering a new composition of matter that eliminates, by precipitation, any free ammonia and masks other curing odors when the product, produced by the process is taken to the “C” stage. The resulting product cures at standard temperatures and conditions while releasing minimal free ammonia.
The inventors are employees of a company that offers, among other coated aggregates, a low hexa coated aggregate that utilizes a novalac resin, plus a liquid resole with the addition of roughly one-half the normal amount of hexa (plus additives). In fact, the low hexa product comprises a 2-stage Novalac system in combination with the single stage “liquid resole” system up to 30% (70% novolac/30% resole), but the past art has not been able to gain adequate crosslink density/or tensile strength without the addition of 6-10% hexa based on resin content. The low hexa product, still using hexa, works well, but still produces a relatively strong odor—mainly ammonia due to the hexa—when the aggregate is brought to the final cure stage (C-stage). Other standard novalac based products exhibit an even stronger odor when brought to the final cure stage. A product formulation showing some of the current art is shown in column 1 of Table 1. For example, it is well understood in the industry that the term hardener refers to the co-reactant or curing agent (such as hexa) and implies the necessary added accelerant (such as salicylic acid). Other examples would include hexa acting as the curing agent combined with a solid resole (such as a phenol-formaldehyde polymer) acting as the accelerant. An example is shown in column 2 of Table 1.
The inventors became aware of buffering solutions used for odor control in the water and wastewater and pulp and paper mill industry (plus others) in which free ammonia is a problem. These buffering solutions are scientifically formulated to react with odorous gases and diluted and applied topically or locally to eliminate malodors in confined spaces and if used outdoors will prevent malodors from traveling to surrounding areas. A review of the literature showed that such buffer solutions had not been tried in sand coating industry (industrial coated aggregates), probably because the effects on the final product were unknown.
Essentially the buffering solution operates under the following chemical equation:
These buffering solutions are generally diluted with water and sprayed in the odorous area as an atomized mist. In water treatment or in the pulp and paper industry, this type of equipment presents no problem. However the in foundry business the additional equipment would be impractical: what was needed was to incorporate the buffer as part of the encapsulation process.
The inventors then experimented with various resin-coated aggregates and associated manufacturing processes. They found that a buffer solution could become a part of the encapsulation process, if the buffer solution were added immediately after the quench water stage of manufacture. They then took samples of the resin-coated sand and drove the samples to the cured (“C”) stage, noting that ‘eureka’ the ammonia odor was almost completely eliminated. Further testing showed that the quality of the resin-coated sand was not affected. That is to say the melt temperature and tensile strength of the buffered product was comparable to non-buffered products.
Furthermore, it was noted in subsequent testing that casting problems due to ammoniacal nitrogen were reduced or eliminated. The reasons for this reduction are straightforward in retrospect. As explained above, free ammonia is produced when the coated aggregate is taken to the “C” stage. The free ammonia is part of the curing process in that the hexa within the encapsulated sand is split into ammonia and formaldehyde in the presence of heat and moisture. It is known that some of the free ammonia is converted to free nitrogen (known as ammoniacal nitrogen) when metals are poured into molds made from these coated cured aggregates as shown in the equations below:
The free nitrogen will pass from the mold into the casting that the mold is set to produce. This free nitrogen can result in a bad casting. Thus, a reduction of ammonia released during the curing process will result in a reduction of free nitrogen that is released during the casting process thereby improving the final cast product.
The inventors found that there were still some residual odors due to some residual ammonia and other by-products such as phenol and formaldehyde. They determined that a masking agent might well remove all traces (actually mask with a pleasant odor) these remaining malodors. A literature search resulted in a suitable agent; however, experimentation was required to determine when the agent should be added and to see if the quality of the resin-coated product was affected by the masking agent. The preferred masking agent is sold as a dry power and can be added with the resin; it can be mixed with water and added after the quench phase with the buffering solution; or it may be added as a powder during the drying stage. Tests determined that the masking agent performed well and that the final quality of the resin-coated sand remained unaffected.
The inventors determined that a product sold by Odor Management, Inc, of Barrington, Ill. under the brand name ECOSORB-303SG was a suitable buffering agent. ECOSORB is an oil based (botanical) product supposedly in which the ingredients are imported from Australia. Essentially ECOSORB is based on organic hydrocarbon plant extract.
The inventors determined that a product distributed by Univar USA, Inc, of Kirkland, Wash. under the brand name VANILLIN was a suitable masking agent. The affects of VANILLIN are not completely understood, although it performs as a masking agent for remaining residual odors such as phenol, formaldehyde, and ammonia. VANILLIN is 4-Hydrox-3-Methoxybenzaldehyde; 3-Methoxy-4-Hydroxbenzaldehyde.
Thus, the inventors discovered that a buffer solution and a masking agent could be included in the formulation of resin-coated sand resulting in a new composition of matter and method of application. The preferred quantity of buffer solution and masking agents are used in a 50:50 ratio and are to be added in direct proportion to the quantity of hexa that was present in the standard formulation which is determined by laboratory experimentation and simple chemical formulation balance.
Finally a series of product test runs was conducted to determine the range of the preferred 50:50 mix to make up the formulation. It was found that the mix could be adjusted favoring the buffer solution (i.e., more buffer than masking agent) and vice-versa. Table 1 shows the range of the constituents of the formulation that result in the NO odor composition of matter of the instant invention.
Thus, the inventors have discovered a new and useful process for the manufacture of a low ammonia emission novalac resin coated industrial aggregate and have further discovered a new composition of matter that reduces any ammonia produced by their novel process to an absolute minimum. Further the instant invention will mask any malodors produced by phenols and the like which appear in novalac system resins.
Thus, it is apparent that there has been provided a composition of matter that comprises a standard formulation for resin-coated sand plus the further ingredients of an ammonia buffering compound and a masking agent added in direct proportion to the quantity of hexa appearing in the standard formulation. There has also been provided a method of manufacture for non-odorous novalac resin-coated sand comprising the addition of a masking agent with the resin, the addition of standard additives, quenching, the addition of a buffering solution and continued mulling to encapsulate the sand. In the alternative, there has also been provided a method manufacture for non-odorous resin-coated sand comprising the addition of resin, the addition of standard additives, quenching, the addition of a buffering solution and masking agent solution and continued mulling to encapsulate the sand. Variations in the order of adding the various ingredients in the instant invention are understood to fall within the spirit of the invention.
While this invention has been described with specific embodiments and its required alternate methods of manufacture, it should be evident that many alternatives, modifications and variations would be apparent to those skilled in the art in light of the foregoing description (in particular the steps taken to determine how to manufacture the invention). Accordingly, it is intended to include all variations as set forth within the spirit and scope of the appended claims.
This application claims the benefit of priority from U.S. Provisional Application 60/801,629 filed on May 18, 2006.
| Number | Date | Country | |
|---|---|---|---|
| 60801629 | May 2006 | US |
