Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2001-11-09
2003-12-02
Cain, Edward J. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C523S130000, C523S131000, C523S132000
Reexamination Certificate
active
06656994
ABSTRACT:
The present invention relates to the use of polysulfide-free preparations comprising at least one water-dispersible copolymer and at least one alkoxylated ionic or nonionic emulsifier, as an additive for construction materials based on loam or clay.
The ready availability and ease of handling of loam and clay have led to their use over many centuries as materials for constructing and decorating buildings, e.g. for producing unburnt loam or clay bricks or tiles, for filling the spaces between the timbers in half-timbered or timber-frame buildings, as renders or mortars, or as filling materials in ceilings or walls. Numerous monographs describe the various techniques relevant for this, for example rammed-earth construction, the production of loam bricks and the processes of loam extrusion and molding. In order to modify the properties of construction materials made from loam or clay, e.g. to improve strength and/or thermal insulation, there are known additives made-from organic materials, such as straw, comminuted wood, shavings, ground cork and/or cellulose, or from inorganic materials, e.g. expanded:slate or shell limestone.
The fact that construction materials of this type made from loam or clay are now of no importance in industrial countries is primarily due to their low compressive strength and low water resistance and to the high degree of shrinkage when construction materials made from loam or clay undergo the required drying. Added to this is the long drying time for these construction materials, since the setting process is essentially physical drying and in most cases takes from 1 to 3 weeks.
A wide variety of possible additives intended to overcome or mitigate these disadvantages is known from the literature, for example, DE-A-41 32 009 formulates a quick-setting mortar mixture based on loam and comprising, in addition to conventional filling materials, a hardener (cement) and also a setting accelerator (gypsum). DE-A-195 42 676 discloses a rapid-hardening mortar mixture based on loam with other .constituents which are cement, a plasticizer and filling materials (expanded clay, perlite, and the like).
Adding cement to construction materials made from loam or clay is frequently problematic-since the two materials differ greatly in their shrinkage behavior during the setting process, and this leads to cracking and therefore severe impairment of mechanical strength. The tendency to cracking can be ameliorated by very slow drying under constant-humidity conditions, further extending setting times.
Addition of organic monomers and/or polymers can also contribute to improving the properties of construction materials with mineral and/or oxidic constituents. For example, JP-A-49099719 describes a construction material based on red loam, an oxidic waste produced in large quantities during the production of aluminum by the BAYER process. This red loam is mixed with cement, sand and from 0.5 to 2% by weight of polymer dispersion and, if desired, water. The example uses 2% by weight of a 40% strength polyvinyl acetate dispersion, based on the total of red loam and cement.
JP-A-58190864 describes colored coating compositions for road construction made from red loam with synthetic resins and aggregates. A synthetic resin which may be used is a 30-80% strength by weight emulsion comprising one or more polymers, such as polyvinyl acetate, polyvinyl acetate-ethylene, polyvinyl acetate-DAAM, polyolefins, polyvinyl chloride and/or epoxy resins. JP-A-49099781 also describes construction materials based on red loam. Here, the red loam is mixed with reinforcing agents or polymer dispersions, molded and dried at 100° C. The resultant construction materials are then degassed under high vacuum, saturated with monomers, e.g. methyl methacrylate containing about 1% by weight of benzoyl peroxide and 1% by weight of silane and then hardened by immersion into hot water. In JP-A-4843051 mixtures of loam with blowing agents, sodium silicate, dolomite, gypsum, perlite and water-repellent silicones with an ethylene-vinyl acetate copolymer emulsion, poly(alkylene oxide) and with an aromatic diisocyanate are prepared, dried using hot air and a microwave dryer and press-molded while hot to give flame-retardant boards of construction material.
U.S. Pat. No. 4,243,563 discloses aqueous compositions comprising calcium polysulfide and to be used for ground stabilization and ground reinforcement. Besides the calcium polysulfide, which is intended to have a reinforcing effect, the compositions comprise a sufficient amount of an emulsifier which is compatible with the calcium polysulfide and facilitates; the penetration of the calcium sulfide into the ground, and a dispersed organic polymer with an average molecular weight of from 5000 to 600,000. The. examples use exclusively vinyl acetate copolymers. The compositions are primarily used for impregnating or saturating ground and construction works, and also for mixing with excavated material, and the mixtures are used, for example, for constructing dams or for producing building blocks for adobe buildings. Any emulsifier is suitable for these compositions as long as it is compatible with the calcium polysulfide, i.e. does not cause this to coagulate.
JP-A-5650156 discloses a process for improving the properties of loamy earth as a construction material by adding from 5 to 40% by weight of an ethylene-vinyl acetate copolymer emulsion with an ethylene content of from 5 to 30% by weight. The ethylene-vinyl acetate copolymer emulsion is prepared by emulsion polymerization under pressure in the presence of a suitable emulsifier and protective colloid. Comparative experiments compared the resultant emulsion with a naturally occurring latex and with an acrylic-based emulsion. To this end all of the dispersions were used to produce sample loam blocks with dispersion contents of from 5 to 20%. The latex and the acrylic-based emulsion proved unsuitable in the comparative experiments, firstly due to insufficient stability of the samples prepared using these comparative emulsions, since in some cases the load-bearing capacity of these samples was less than 50% of that of samples produced using ethylene-vinyl acetate emulsions, and secondly due to the unpleasant odor observed from these samples with the comparative emulsions. In comparison with the use of untreated loam a disadvantage of this process is that the ethylene-vinyl acetate copolymer emulsions are detrimental to ease of use, i.e. the adjustment of the consistency of the loam/emulsion mixture and its subsequent handling, e.g. the conveying and molding of the mixture. In addition, some of the construction materials prepared by this process have an even higher degree of shrinkage than pure loam during setting.
It is an object of the present invention to provide an additive which improves the mechanical strength and the water resistance of construction materials based on loam or clay and which is easy to use, i.e. easy to incorporate into the construction materials, and has good properties during the further handling of the construction materials, and does not require additional hardening steps, such as heating, irradiation, etc. The undesirable shrinkage during setting, as typically found when using construction materials based on loam or clay, should be reduced.
We have found that this object is achieved, surprisingly, by an additive for construction materials, in particular for unburnt construction materials based on loam or clay, which overcomes the disadvantages of the prior art, gives the construction materials high mechanical strength and water resistance and provides ease of use. Constituents present in the additive are a water-dispersible copolymer and from 0.5 to 10% by weight of at least one alkoxylated ionic or nonionic emulsifier.
The present invention therefore provides the use, as an additive for construction materials based on loam or clay, of polysulfide-free preparations comprising, based on solids content, from 40 to 99.5% by weight of at least one water-dispersible copolymer and from 0.5 to 10%
Boettger Karl-Georg
Dreher Stefan
Knöfel Dietbert
Pakusch Joachim
Roser Joachim
BASF - Aktiengesellschaft
Cain Edward J.
Lee Katarzyna Wyrozebski
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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