Stock material or miscellaneous articles – Sheet including cover or casing – Including elements cooperating to form cells
Reexamination Certificate
1999-12-17
2002-02-05
Jones, Deborah (Department: 1773)
Stock material or miscellaneous articles
Sheet including cover or casing
Including elements cooperating to form cells
C428S116000, C052S793100, C052S310000, C052S102000
Reexamination Certificate
active
06344253
ABSTRACT:
TECHNICAL FIELD
The present invention relates to the technical field of building of habitations and/or factories, as well as of more complex building works such as building of tunnels, submarine structures and the like.
More particularly, the present invention aims to provide for a leakproofing article to be used in the building of habitation and or factory structure foundation, or for building of underground structures and/or tunnels, as well as in the more difficult technical field of submarine works.
The present invention may be mainly applied in the general technical field of building.
BACKGROUND ART
The use of bentonite as leakproofing material in the field of building is well known in the art.
For instance, it is used in the building of foundation and/or in any other type of application in which a suitable degree of imperviousness to water has to be assured.
It is also known that sodium natural bentonite is a clay which undergoes a substantial hydration when it comes into contact with water, said hydration increasing the bentonite volume up to thirty times its dry volume.
As a consequence of the hydration process, it is known that the bentonite produces both a gel phase of the colloidal type, which causes an increase of the bentonite volume of about 10-15 times with respect to its dry volume, and a solute phase, which causes an even greater increase of the bentonite volume.
Bentonite is used in the form of particles, generally placed inside of one or more layers of corrugated card-board sheets or of needled non-woven fabrics, obtaining a structure similar to a panel and/or a small mattress which is set at the extrados of underground structures foundation and/or at any other location where a leakproofing barrier is needed.
A further solution known the art provides for the use of bentonite coupled with a suitable binder, e.g. butylic rubbers and/or water-soluble glues.
In this case, the system binder/bentonite is given a rolled shape or a panel type shape to so that it can be sufficiently handy and easy to be laid.
For instance, U.S. Pat. No 4,048,373 discloses a solution of the type cited above according to which a leakproofing panel is produced, said panel being formed by two sheets, advantageously card-board sheets, suitably spaced in order to contain bentonite together with a suitable additive.
In general, said additive is constituted by a water-soluble dispersant, e.g. a water-soluble salt of acetic or phosphoric or boric acid, combined with a water-soluble polymer, for instance polyacrylic acid, water-soluble salts of polyacrylic acid, polyacrylnitril, polyvinylacetate, polyvinylalcohol or copolymer thereof, according to defined percentages of the components of the bentonitic composition.
According to a preferred form of embodiment disclosed in U.S. Pat. No. 4,048,373, the leakproofing panel is constituted by two corrugated card-board sheets and by a corrugated paper band which is placed between them.
Said paper band comes into contact with the two sheets forming a plurality of voids which are filled with the bentonitic composition mentioned above.
U.S. pat. No. 4,048,373 discloses a water impervious panel comprising one upper and one lower sheets, said sheets being made of one of one of a range of polymers. A shortcoming of the above document is that the dissolution rate is not predetermined and controlled, theref ore there may be found to occur the expansion of the bentonite pack at undesired times, and the only thing that can be relied upon in that respect is carrying out the operations in an extremely expedite way, which is not always possible whereas it is always to the detriment of accuracy and safety, and does not rule out t he risk that the expansion takes place when the panels are still being worked upon.
Moreover, the panel disclosed in the above document is not structurally feasible, as the water swellable material is simply laid upon its solid support, therefore it is prone to structural failure.
In the present application the bulk impermeable material is found to be spread over an inner layer made of biodegradable kraft paper that has characteristically such a shape that it confers the device an overall inherent resilience and resistance, therefore a particular suitability for use in the building industry as there are no risks for it to suffer from structural failures even when the water swellable material has not set.
Furthermore, the dissolution rate of the coating can be controlled with extreme precision.
EP-A-567,692 discloses a clay-based impermeable material to be used in the building industry, made of sodium or calcium bentonite, and applied to a support, said material fulfilling its function on account of the fact that the sodium or calcium bentonite is coated with a degradable and temporarily water resistant coating, made of cellulose. The durability of the coating disclosed in the above document depends on its thickness, as after contact with water, it breaks down at a constant rate. Therefore if a material with a relatively long temporary surface impermeability is desired, then encumbering volumes of the surface coating must be used, thing which in certain cases may turn out to be detrimental for the stability of the whole building, as, after dissolution, free voids are left to bear considerable weights. Another shortcoming of the disclosure of the above document is that because the bentonite is simply laid upon its support, it is inherently of limited resilience and resistance.
In other words, this document does not disclose any means for keeping under control the water-solubility of the material constituting the coating layer of the leakproofing article.
U.S. Pat. No. 4,565,468 discloses a device for providing a moisture impervient barrier comprising a base sheet member with a bentonite layer on its upper surface, and a top sheet member positioned over the bentonite.
The top sheet member is constituted of a material pervious to water so as to permit hydration of the bentonite.
The present invention aims to solve the problem constituted by a quick, premature and uncontrollable hydration undergone by granular sodium bentonite when it contacts water, which can be rain water and/or water coming from a water-bearing stratum or from concrete, during particular structure building steps.
Said casual and premature bentonite hydration is often extremely negative as regards to the final result of the structure which has to be built and to the realization of an effective leakproofing barrier.
In fact, if the bentonite hydration process occurs before the concrete structure is laid, and the obtained structure can result as being defective; the consequent effects deriving therefrom can be deleterious for the building.
On the other hand, if the bentonite hydration occurs when the concrete has just been cast, the increase in the bentonite volume can exert a harmful pressure on the concrete which does not have a sufficiently high mechanical resistence yet, thereby causing permanent damages to the building structure.
Furthermore, it may happen that the hydrate bentonite, i.e. the expanded bentonite, soils and muddies the concrete reinforcements causing adhesion problems which determine the iron being uncoupled from the concrete, which phenomenon is known under the name of reduction or zero setting of the iron/concrete matrix.
Thus, said drawbacks produce remarkable and often irreversible damages both to the leakproofing system and to the structure which has to be built.
This means that works must be stopped and a new leakproofing barrier made of bentonite is needed to be laid, thereby causing a loss of time and an increase of the costs.
The realization of water-soluble plastic and completely biodegradable films, e.g. films based on polyvinylic alcohol (PVOH), to be used in very different applications, is also known in the art.
For instance, said articles can be advantageously used as protective colloids of numerous chemical components, particularly in paper and textile fields; as light polarizing filters; as temporary sizes in textile yarns production; as mai
Boss Wendy
Jones Deborah
Oppenheimer Wolff & Donnelly LLP
LandOfFree
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