Compositions: coating or plastic – Coating or plastic compositions – Contains fireproofing or biocidal agent
Reexamination Certificate
2000-11-27
2003-01-07
Green, Anthony J. (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Contains fireproofing or biocidal agent
C106S277000, C106S281100, C106S283000, C106S284000, C424S405000, C427S298000, C427S393000, C427S442000, C514S762000
Reexamination Certificate
active
06503306
ABSTRACT:
This invention relates to compositions of the oil and water emulsion type for the impregnation of porous materials. The compositions of the invention are particularly useful in the preservation of porous materials such as timber.
BACKGROUND OF THE INVENTION
Known compositions of the above type in particular those which use creosote or protecting agent based on tar oil have turned out to the very disadvantageous since especially in case of the impregnation of timber a so-called “bleeding” occurs after completion of the impregnation process This bleeding occurs for example due to the influence of weather, particularly in hot weather, and during repair and may persist for years. During this bleeding oil diffuses to the surface of the impregnated material. Thus, for example, greasy tar coatings form at the timber surface, if composition containing tar oils are used for impregnation. These tar coatings can cause problems during the handling of the timber and can have an unhealthy effect when getting in contact with the skin, at least they can cause irritations of the skin and, due to volatile components of the oil, also the eyes. As the timber surface will never become completely dry these drawbacks will always remain.
The bleeding of the impregnated timber is substantially enhanced by heating of the timber during exposure to sunlight. The emissions of the timber, which especially occur then, can cause the skin of sensitive persons to become red, similar to a sunburn.
It has been proposed to avoid these drawbacks by using pigment-stabilised emulsions, in which it appears that the pigments block diffusion of the oil. The mechanism which is the basis for the blocking is not yet exactly understood, however, there are indications that it is the large contact angle between the oil and the discrete pigment particles, which are embedded within the microstructure of a material treated under pressure. Thereby wetting of the pigments by the oil becomes more difficult or even impossible, since no coalescence of the pigment particles occurs during the impregnation process or when the emulsion breaks and lipophobic particles become embedded within the pore structure of the material being treated.
The invention addresses the problem to provide an impregnation means that penetrates very easily into the substrate to be treated, that distributes well in this substrate and reduces or eliminates the bleeding of oil very effectively from the impregnated material.
THE PRESENT INVENTION
The present invention provides composition for impregnating porous materials, in which the composition contains at least one component having preservative properties or which releases a component having preservative properties on heating, the composition comprising an emulsion of water and oil containing a primary surfactant and an amphoteric additive, the pH of the emulsion being equal or approximately equal to the iso-electric point of the. amphoteric additive.
In one aspect of the invention the emulsion contains at least one amphoteric additive which does not act as an emulsifier. In case only one amphoteric additive is present, the pH-value of the emulsion is equal or nearly equal to the iso-electric point of the amphoteric additive. If the emulsion contains several amphoteric additives, the pH-value of the emulsion is adjusted so that it is within or nearly within the range of the iso-electric points of the additives, i.e. the pH-value is adjusted so that it is optimised with respect to the iso-electric points of the additives. This can be achieved for example by adjusting the pH-value to be equal to the mean value of the various iso-electric points. However, if the amphoteric property of one of the additives is of an especially high importance the pH-value can also be equal to the iso-electric point of this additive or be close to the iso-electric point thereof, respectively. With regard to this it is to be considered that such an additive also at a pH-value of the emulsion which is not exactly, however nearly equal to the iso-electric point, exhibits the property of the electrical neutrality in so far as the additive component always comprises a portion of particles which appear neutral, and always a portion of particles which do not appear neutral. In this case the amount of the respective portion is dependent on the pH-value of the emulsion. At the pH-value of the emulsion which is equal to the iso-electric point, the portion of the particles which do not appear neutral is zero.
Thus, it is achieved that the additive or the additives appear electrically neutral or nearly electrically neutral, respectively. Since in general the material to be treated is charged, in this way it can be achieved that the additives penetrate better into the material. An undisturbed flow of additives can take place within the micro-structure of, for example, timber types or materials based on timber, without coalescence occurring, i.e. an accumulation of additives. Thus, the additive particles can be embedded individually into the micro-structure of the materials being treated, in fact discretely when the emulsion breaks.
Especially, this impregnation according to the invention is very advantageous in the treatment of timber. Since timber is charged negatively, for this reason during the application of conventional impregnation means several parameters have to be observed. Using the impregnation means according to the invention, with regard to these parameters now a simplification and considerable improvement is achieved. Thus it is possible to apply the impregnation means according to the invention with a smaller pressure and during a shorter period of treatment. Furthermore, also the temperature of the impregnation means can be decreased, because due to the reduction or elimination of electrical interaction between the timber and the penetrating additive, one can work with a higher viscosity of the impregnation means. Thus the substrate can be impregnated with substantially less consumption of energy and time.
The additives can be particles which consist of two or more constituents, of which one is an amphoteric surfactant. In this case the amphoteric property of the additive is given by the surfactant. The surfactant promotes the penetration and the distribution of the additive within the material to be treated.
The impregnation means according to the invention develops its advantageous properties especially if a pigment is used as amphoteric additive. The amphoteric property can be achieved in that the pigment is surface activated with an amphoteric surfactant, or in that the pigment itself is amphoteric.
Because of the fact that the pigment appears uncharged, its property is enhanced to prevent the outflow of oil from the inside of the material to be treated to the surface thereof. The reason for this could be that the contact angle is increased, whereby a wetting of the pigment by the oil is still further decreased. Moreover, due to this neutrality the pigment does not react with water or other chemicals contained within the material to be treated, so that the lipophobic property and thus the effect to block the outflow of oil out of the material is not impaired. This is the case both when the water contained in the emulsion evaporates quickly after the treatment of the material, and when the emulsion is broken by the evaporation of the water but also through external influences—as for example rain—water gets to the surface of the treated material. In both cases the pigment does not react with the water, i.e. it remains dry and fully keeps its property to block the outflow of oil, even if the pigment is recharged in the course of time.
Instead of the pigment also an inert filler or several fillers can be constituents of the emulsion. This inert filler exhibits essentially the same advantages as the pigment and can also be activated either with an amphoteric surfactant or can itself be amphoteric. With regard to the positive effect concerning the prevention of outflow of oil from the material to be treated the same is valid as f
Green Anthony J.
James Ray & Associates
Monash University Act 1958
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