Stock material or miscellaneous articles – Hollow or container type article – Polymer or resin containing
Reexamination Certificate
1999-04-14
2003-05-20
Pyon, Harold (Department: 1772)
Stock material or miscellaneous articles
Hollow or container type article
Polymer or resin containing
C428S034100, C428S034400, C428S035800, C428S413000, C428S426000, C428S402000, C428S404000, C523S200000, C523S513000, C524S261000, C524S315000, C524S400000, C528S093000
Reexamination Certificate
active
06565935
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to polymer concrete structures in the form of vessels, cells or other containers or components of a type that may be used, for example, for containing or use with acid solutions, especially heated acid solutions e.g. electrochemical cells.
Polymer concrete refers to compositions that are formed from thermosetting polymers and aggregates, especially in which the aggregate is particulate siliceous fillers e.g. sand, gravel, quartz stones and the like.
BACKGROUND OF THE INVENTION
Polymer concrete is particularly intended for use in the forming of a variety of structures that are exposed to corrosive environments and/or which are subject to abrasive environments. The corrosive environments may be atmospheric conditions in which the structure would be exposed to acids that exist in the atmospheric environment. In other embodiments, the polymer concrete is intended for use in the formation of vessels that are intended to contain corrosive chemicals, for instance acids.
One end-use for polymer concrete compositions is in the field of electrolytic recovery of metals from corrosive metal-bearing acid solutions. Techniques for the recovery of metals from ores or concentrates frequently involve the use of electrolysis, often using warm or hot acidic solutions. The warm or hot acidic solutions are contained in vessels, known as cells, that have a plurality of rows of electrodes, which are alternately anodes and cathodes. Electrolytic deposition of the metal is effected from the electrolyte onto the cathode. The electrolyte is almost invariably an acid solution of a type which can be highly corrosive to materials from which the container or cell is formed.
Cells were traditionally produced from concrete, with a chemically-resistant non-bonded liner incorporated inside the tank. However, such liners did not provide long term protection for the concrete. Damage to the liner e.g. cracks and holes, resulted in penetration of hot acid through the liner to the concrete, and the likelihood of catastrophic deterioration of the concrete cell. Maintenance costs were very high.
Concrete cells with liners have been replaced with cells formed from polymer concrete compositions of vinyl ester polymers and aggregate blends, the latter normally being siliceous material in a particulate form e.g. sand or gravel. These polymer concrete compositions typically have 10-12% by weight of polymer. While cells formed from vinyl ester resins/aggregate blends are a significant improvement over lined concrete cells, it was found that cracks occur in the manufacture of the cell i.e. in the so-called pre-cast product, necessitating repair and complete coating of both interior and exterior surfaces with a high build/high polymer content layer before the cell can be released for use in an electrochemical process.
The tendency for cells made from vinyl ester resin/aggregate blends to crack during casting results in the need to provide internal coatings for such tanks, and/or to effect repairs on site after installation but before use of the cell. The need to provide coatings and repairs is both time consuming to the manufacturer of the cell and to the user of the cell, and an added expense in the manufacture and supply of such cells. While these cells represent a significant improvement over previous cells, the need to conduct repairs prior to use partially defeats the intent and gains to be obtained from use of polymer concrete compositions.
In addition to the use of polymer concrete compositions in electrochemical cells, there are other structures that require protection against acidic environments or abrasive conditions, in which traditional concrete is susceptible to the environment and where additional protective layers are required or could be beneficial. Such other structures could include beams, channels, curbs, drains, chutes, pipes, floors and structures that require chemical and abrasive protection, compared to traditional concrete.
Polymer concrete compositions that are intended to be used in environments that are exposed to corrosive chemical attack are known. For instance, U.S. Pat. No. 4,621,010 and related EP 0 170 740 are directed to composite materials suitable for use in making containers or structures exposed to corrosive chemical attack, which are formed by mixing a synthetic resin material with two different hardeners and employing a filler of particulate siliceous material e.g. sand, gravel, quartz stones or the like. A skin coat formed from the same resin but using a filler with a fine particle size of less than 0.5 mm may be added, which permits use of larger particles, such as 6 mm and above, in the formation of the cell. Typical sizes of the filler were stated to be about 40% by weight of total filler in the range 0.5-1 mm, with other fractions including about 15% by weight in the range 1-1.75 mm and a further 15% by weight in the range 1.75-3 mm. It was found that larger particles, up to 6 mm, imparted strength to the structures that had been formed.
SUMMARY OF THE INVENTION
A polymer concrete structure has now been found that is resistant to acid solutions.
An aspect of the present invention provides a structure for resisting acid solutions, said structure being formed from a filled thermosetting polymer composition comprising a mineral filler in an amount of at least 92% by weight and not more than 8% by weight of thermosetting polymer, said composition containing a wetting agent, said composition having a co-efficient of thermal expansion that is less than 15×10
−6
in/in/° F., the filler being a mineral particulate filler with generally rounded edges and the thermosetting polymer composition having a density that is at least 95% of the theoretical density for said filler and polymer, the filler being comprised of at least 50% by weight of a particle size that is greater than 6 mm, at least 70% by weight of a particle size that is greater than 2.4 mm, and at least 85% by weight of a particle size that is greater than 0.4 mm, the thermosetting polymer being obtained by reaction of (a) an epoxy resin formed from at least one of Bisphenol A and Bisphenol F with (b) an amine selected from at least one of an aliphatic and a cyclo-aliphatic amine.
A further aspect of the present invention provides a vessel for resisting acid solutions, said vessel being formed from a filled thermosetting polymer composition comprising a mineral filler in an amount of at least 92% by weight and not more than 8% by weight of thermosetting polymer, said composition containing a wetting agent, said composition having a co-efficient of thermal expansion that is less than 15×10
−6
in/in/° F., the filler being a mineral particulate filler with generally rounded edges and the thermosetting polymer composition having a density that is at least 95% of the theoretical density for said filler and polymer, the filler being comprised of at least 50% by weight of a particle size that is greater than 6 mm, at least 70% by weight of a particle size that is greater than 2.4 mm, and at least 85% by weight of a particle size that is greater than 0.4 mm, the thermosetting polymer being obtained by reaction of (a) an epoxy resin formed from at least one of Bisphenol A and Bisphenol F with (b) an amine selected from at least one of an aliphatic and a cyclo-aliphatic amine.
DETAILED DESCRIPTION OF THE INVENTION
The present invention utilizes a polymer concrete composition which is a filled thermosetting polymer composition having a mineral filler content of at least 92% weight. Conversely, the composition contains not more than 8% by weight of the thermosetting polymer. In preferred embodiments of the invention, the polymer concrete composition contains 92-94% by weight of the mineral filler, and correspondingly 6-8% by weight of the polymer.
The thermosetting polymer may be varied depending on the particular conditions of use of the resultant structure e.g. the chemical or abrasive environment that the structure would encounter during normal use. Preferred ex
Caesar Rivise Bernstein Cohen & Pokotilow Ltd.
Cappar Limited
Patterson Marc
Pyon Harold
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