Drug – bio-affecting and body treating compositions – Designated organic active ingredient containing – Phosphorus containing other than solely as part of an...
Reexamination Certificate
2000-10-17
2004-04-13
Pryor, Alton N. (Department: 1616)
Drug, bio-affecting and body treating compositions
Designated organic active ingredient containing
Phosphorus containing other than solely as part of an...
C514S231200, C514S299000, C514S307000, C514S383000, C514S394000
Reexamination Certificate
active
06720313
ABSTRACT:
TECHNICAL FIELD
This invention relates to fungicides and is intended particularly to provide a fungicidal composition and/or a method of preparing a fungicidal composition, particularly but not exclusively for application to lignocellulosic substrates so as to confer an antifungal characteristic to logs, lumber or other products derived from said lignocellulosic substrates and to other organic substrates such as leather products and paint.
BACKGROUND ART
Whilst still alive and growing, trees, suitable for conversion to lumber or other lignocellulosic products, are relatively immune from or are self protecting against fungal attack. After felling logs are immediately vulnerable to attack due to cutting or bark damage due to colonisation by fungi. Damage to the substrate initially appears as visual degrade (due to pigment formation by the fungi) which lowers the value of the substrate but later this may also lead to physical degrade which may negate the value of the substrate. To protect these or products derived from them from degradation it is common practice to treat these with aqueous fluids containing fungicides (biocides).
Historically a wide range of fungicides has been used including toxic substances such as sodium pentachlorophenate, trichlorophenol, and mercury compounds. Modern prophylactic formulations generally use less toxic compounds although those more toxic are still used in some cases. Often when cost is a major consideration, and more so in less developed countries, more hazardous compounds continue to be used. Where cost is an issue, a more competitive formulation will offer a viable option.
More recently the lumber industry has been looking closely at prophylactic formulations to further reduce any potential threat and in doing so has been scrutinising formulating aids typically used in these formulations. Some concern is evident regarding certain solvents, and other additives have been recognised as posing a threat to workers using these products.
Traditionally prophylactic treatment formulations have been formulated such that they, by design or default, adhere to, fix to or precipitate at the surface of the substrate.
For example, one of the earlier biocides used, pentachlorophenol was formulated at a high pH, as the sodium salt of the otherwise relatively insoluble pentachlorophenol. Upon application to the substrate as an aqueous solution the pentachlorophenol would precipitate due to the buffering action of the wood which has a natural pH of approximately 4.0. Although highly toxic, pentachlorophenol did have an advantage over most modern biocides in that it has a high vapour pressure so was able control fungal degrade remote from the point of application by fumigant action.
U.S. Pat. No. 4,950,685 to Kop-Coat teaches the formulation of a synergistic prophylactic formulation comprising dodecyl dimethyl ammonium chloride (DDAC) and iodo propynyl butyl carbamate (IPBC) as co-biocides. In this case, for example, when applied to wood, DDAC will fix to the wood surface by an ion exchange mechanism and since the DDAC, which acts as a surfactant solubiliser for the IPBC, has been deactivated by binding to the substrate, the IPBC, which has low solubility in water, precipitates at the surface also.
U.S. Pat. No. 1,571,814 to Chapman Chemical teaches the solubilisation of copper 8-hydroxyquinolinolate using various strong organic acids. The biocides of this invention have good efficacy and are relatively inexpensive. The acids used however are corrosive to metals that may be involved in the containment of the formulations during use, add significantly to cost, cause foaming (which is inconvenient and potentially hazardous) and may be toxic to workers exposed to the product. The mechanism of fixation in this instance also relies on the natural buffering pH of the substrate (4.0) wherein the treating solution with a pH normally around 2.5 to 3 will precipitate the copper 8-hydroxyquinolinolate when the pH increases to 4.0 on the substrate surface. It has been well documented that copper 8-hydroxyquinolinolate completely precipitates when the pH is greater than 3.3 (Arthur I. Vogel. A Text-book of Quantitative Inorganic Analysis, Third edition 1966 Longmans).
Similarly NZ Patent 225428 to Chemicca describes an organic solvent based formulation combining copper 8-hydroxyquinolinolate (frequently referred to in the art as “oxine copper”) and carbendazim (methyl benzirnidazoyl carbamate) using dodecyl benzene sulphonic acid as a solubilising agent. The principle of solubilisation and precipitation of this formulation is the same as that of U.S. Pat. No. 1,571,814 except that carbendazim requires higher levels of acid to solubilise the additional biocide. This leads to an additional disadvantage for this type of formulation in that it is more expensive and in that the carbendazim precipitates more readily. This occurs where contamination of the treating solution occurs with natural salts from the source of water, or chemicals from the wood itself leach into the treating solution, raising the pH to a point where the carbendazim begins to precipitate prematurely. This leads to agglomeration of carbendazim particles and, and eventually to changes in the rheology of the solution making the product difficult to use and in some cases, for example, when it may be sprayed, impractical to use. The formulating aids used in this type of formulation are costly and also impose an additional biological load on the environment. Foaming of the product in use is frequently a problem.
Many other products have been produced for this market including suspension concentrates or flowables wherein the insoluble biocides are ground to a very small particle size (less than 10 microns) and then stabilised in suspension using various aids. These formulations are expensive to produce but more significantly precipitate during use necessitating continuous vigorous agitation, and are precipitated at the wood surface by a filtering action.
It is now being more widely recognised that certain fungal species, which colonise wood and derivatives, grow remarkably rapidly (for example many of the Ophiostoma species) and can penetrate into the substrate from the surface at an easily detectable rate. Wood and many other natural products are very rarely treated with prophylactic materials at the time of initial production and therefore may be well colonised by degrading organisms before any biocide is applied. It is therefore logical that these organisms may be well out of reach of, and therefore are unable to be controlled by, any biocide that precipitates or remains very close to the surface of the substrate. This is now well recognised by those working in the industry. Historically pentachlorophenol and trichlorophenol were able to achieve a level of control by the fumigant action previously mentioned.
Unfortunately pentachlorophenol and trichlorophenol have generally been prohibited from use due to its high toxicity. Few other fungicides have a similar action and those that do are also acutely toxic such as methylene bis-thiocyanate.
There is a need therefore for a prophylactic treatment system that allows the biocide or biocides to penetrate further into the substrate prior to precipitation. Very strong acids can be used to dissolve many of these biocides but they are hazardous, can destroy the wood substrate and will certainly aggravate any corrosivity.
Although preferred fungicidal actives are now being chosen from a group having very low toxicity, other components still pose problems. These include those used in the aforementioned patents and can be summarised to include;
high toxicity to users (by ingestion, skin contact or inhalation)
high levels of irritation
strong offensive odour
corrosivity to metals
high levels of foam formation
poor physical properties leading to improper application such as:
high viscosity
precipitation and agglomeration of actives
a poor rheology leading to poor spraying
loss of actives during recovery and recycle.
Formulating aids that have been used to solubilise biocides
Jacobson & Holman PLLC
Mattersmiths Holdings Limited
Pryor Alton N.
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