Compositions: coating or plastic – Coating or plastic compositions – Inorganic settable ingredient containing
Reexamination Certificate
2000-12-12
2003-09-09
Brunsman, David (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Inorganic settable ingredient containing
C106S730000, C106S205900, C106S823000, C536S123120
Reexamination Certificate
active
06616754
ABSTRACT:
This application is a 371 of PCT/FR00/00245 filed May 4, 2000.
FIELD OF THE INVENTION
The present invention relates to a segregation reducing agent prepared by alkalifying a curdlan-producing fermentation broth per se or a curdlan powder in solution with alkaline material, and also relates to hydraulic compositions, concrete and mortar, comprising the segregation reducing agent. This segregation reducing agent can provide a great resistance to segregation for hydraulic compositions even at its small amount as well as guarantee the strength, filling ability and fluidity.
BACKGROUND
As main concrete materials, there are specifically enumerated cement, water, fine aggregate and coarse aggregate. However, recent increasingly intensive interest in the high strength and durability of concrete as well as in the economizing of construction with concrete has directed active research toward the development of admixtures capable of providing a variety of functions to concrete. Such admixtures may be representatively exemplified by an AE agent (air entrainment agent), a water-reducing agent and an AE water-reducing agent. Offering a variety of functions, including the improvement of concrete workability, the augmentation of resistance to freezing and thawing, the reduction of the cement amount to be used by virtue of water reducing effect, and the strengthening of concrete strength, the admixtures are recognized as the fifth ingredient for concrete. Generally, the water-reducing agent can bring about a reduction of water by 10 to 30%. However, overuse of the water-reducing agent makes worse the physical properties of concrete, as in the increase of air entrapment and the segregation of the material ingredients.
With he aim of repressing these side effects, polysaccharides have been added as an admixture for concrete. They function to enhance the viscosity of concrete, so as to suppress the segregation of material ingredients and increase the fluidity of concrete.
It is known that a broad spectrum of microbes is able to produce polysaccharides. Polysaccharides that microbes extracelluarly secrete are quite different in terms of molecular weight, kinds of constitutive sugar units, the order, type and position of the linkages between sugar units, and the existence of branches, depending on strains and culture methods. They also exhibit different gelability, emulsion stability, surface tension controllability, water absorptivity, tackifying property, lubricating ability, and. film forming property from one another. Numerous applications of polysaccharides, which are mainly produced from microorganisms, exist in the food, cosmetic, petroleum and paper industries. For instance, they are used as stabilizers, emulsifiers, and thickeners in the food industry. Also, they are useful for excavating or crude petroleum-recovering processes in the petrochemical industry. In addition, polysaccharides have recently been applied for the drag reduction for ships and to make high value-added bio-medicines as well as being newly developed as admixtures for construction.
Curdlan, which
Agrobacterum spp
. and
Alcaligenes faecalls
secrete from these cells into an extracellular space, is a water-insoluble, neutral polysaccharide which consists of glucose units bonded to each other through beta-1,3-glycosidic linkage. This homopolymer shows a characteristic physicochemical property of irreversibly forming gel when being heated, so that it is added as a thickener for foods. Thus, the polysaccharide finds numerous applications, including jelly foods, food fibers, film and immobilized carriers (Paul et al.,
Biotechnol. Adv
., 4:245-259, 1986). Particularly, there are disclosed many patents pertaining to use of curdlan as segregation reducing agents for concrete materials.
For example, Korean Pat. No. 144454 (1998), yielded to Daisei Construction. Co. Ltd., Japan and Takeda Chemical Industries, Ltd., Japan, discloses that a powder of beta-1,3-glucan is added to increase the viscosity of a hydraulic composition comprising a binder to suppress the segregation among the materials of the composition and enhance the fluidity of the composition. However, the quantity of curdlan used in the reference patent amounts to from at least 1.36 to 2.96 kg per unit volume (m
3
) of concrete, giving rise to a large increase in the cost of concrete.
Takeda Industries Ltd., Japan, also discloses in U.S. Pat. No. 5,376,173 a segregation reducing agent which is obtained by adding a highly viscous polysaccharide such as xanthan or methylated cellulose to a culture of a microorganism capable of producing curdlan and drying the mixture to give a powder. In this segregation reducing agent, the employed polysaccharides, that is, a mixture of curdlan and another polysaccharide amounts to as much as 1.6 kg/m
3
of concrete, suffering from a disadvantage of increasing the production cost of concrete.
U.S. Pat. No. 5,573,589 describes chemical modification of curdlan in which curdlan is treated with sulfate (SO
3−
) to produce curdlan sulfate which is then used as an admixture for concrete. However, the curdlan used for the preparation of the curdlan sulfate amounts to from as much as 1.75 to 3.15 kg/m
3
of concrete, depending on the uses of the modified curdlan.
In the prior arts described above, a powdering process is required for curdlan or its derivatives to be used as a segregation reducing agent for concrete, giving rise to an increase in the production cost, there is needed a collateral cost for the derivatives or auxiliary additives serving to enhance the viscosity of concrete, and the powder should be added at an amount of as much as 1 kg per lube (m
3
) of concrete in order to show an effect as a segregation reducing agent.
Thus, there remains a need for developing a segregation reducing agent which is simple in its preparation and has a great effect even at a small amount, thereby reducing the production cost.
Leading to the present invention, the intensive and thorough research on segregation reducing agents for hydraulic compositions, repeated by the present invention aiming to use curdlan with a great economical advantage, resulted in the finding that the alkalifying of curdlan powder or a curdlan-producing fermentation broth gives a curdlan solution of high viscosity which brings about a maximal effect in the resistance to segregation with its small amounts and that use of the curdlan-producing fermentation broth itself can eliminate the cost for powdering equipments and processes.
SUMMARY OF THE INVENTION
It is an object of the present invention to overcome the above problems encountered in prior arts and to provide a segregation reducing agent for a hydraulic composition, which brings about a great improvement in resistance to segregation with an economical advantage.
It is another object of the present invention to provide a hydraulic composition containing such a segregation reducing agent.
Based on the present invention, the above objects could be accomplished by a provision of a segregation reducing agent for hydraulic compositions, comprising curdlan and an alkaline material.
Also, in accordance with the present invention, there is provided a hydraulic composition comprising such a segregation reducing agent.
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, curdlan is obtained from a fermentation broth which contains sugar or raw sugar as a carbon source and ammonium chloride as a nitrogen source, in combination with other inorganic salts. As microorganisms grow in the medium, curdlan is secreted from the cells. Preferably, although not necessarily, the curdlan may be purified for use.
Purification of raw curdlan is carried out as follows. A fermentation broth highly rich in curdlan is controlled in neutral pH during growth and production phase. Since curdlan is not dissolved in a neutral solution, curdlan exists as a water-insoluble form. The fermentation broth is alkalified to solubilize the curdlan which is then able to be separated from the cells by centrifugation or filtration. After removal of
Jung Kyung-Hee
Kim Mi-Kyoung
Lee In-Young
Lee Jung-Heon
Park Young-Hoon
Bachman & LaPointe P.C.
Brunsman David
Korea Research Institute of Bioscience and Biotechnology
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