Compositions: coating or plastic – Coating or plastic compositions – Inorganic settable ingredient containing
Reexamination Certificate
1998-08-07
2003-01-07
Marcantoni, Paul (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Inorganic settable ingredient containing
C106S738000, C106S753000, C106S754000, C106SDIG007
Reexamination Certificate
active
06503319
ABSTRACT:
The invention relates to a method for preparing a mortar which contains a fraction of inorganic grains having a diameter <500 &mgr;m.
The term mortar refers to a mixture which contains a binder, a filler, preferably sand, and water.
There is a need for admixing mortar, for example concrete mortar, with a fraction of inorganic grains having a diameter <500 &mgr;m, hereinafter referred to as fine fraction. As a result the total filler content of the product which is prepared from the mortar, such as, for example, concrete or sand-lime brick can increase, and the mechanical properties of the product are improved. This also makes it possible for a smaller amount of binder such as, for example, cement, to be added to the mortar, while the product which is formed from the mortar still has adequately good mechanical properties.
A problem in the preparation of such a mortar is that the fine fraction, which is generally added separately from the other fillers, mixes only very slowly and often incompletely with other components of the mortar. Consequently the advantages which could be achieved by the addition of the fine fraction are not or only partially achieved. Thus it is then again often necessary to add an excess of binder to the mortar, the drawbacks being that the product prepared from the mortar is less durable, suffers from increased shrinkage and has a higher cost price.
Solutions to the above-mentioned problem have been sought in the past, without a solution having been found with which the desired result was achieved.
It is an object of the present invention to provide a method for preparing a mortar which does not have the abovementioned drawbacks.
This object is achieved, surprisingly, by the fine fraction, in the method according to the invention, being added in-the form of a granular material which contains the inorganic grains fraction, which grains, with the aid of a water-soluble polymer, are bound so as to form the granular material.
This ensures that the fine fraction is mixed rapidly and well, so that a homogeneous mortar is obtained.
A further advantage is that the granular material can be readily handled, whereas the fine fraction as such, for example fine sand, is virtually impossible to handle. When transferred, the fine sand will dust and thus presents a health hazard. Moreover, the fine sand is very cohesive and therefore agglomerates and causes bridging in the hopper of a storage vessel, whereupon the sand is unable to flow through the hopper. The granular material in contrast can be readily handled, does not dust and easily flows through a hopper. Furthermore, the mortar which contains the fine fraction of the inorganic grains can be prepared in a simple manner with the aid of the methods and equipment known therefor, because the water-soluble polymer which binds the grains so as to form the granular material dissolves in the water of the mortar.
EP-A-0 587 383 is describing aglomerates of cement particles. The cohesion of the particles in the agglomerates is insufficient. Further EP-A-0 587 383 does not disclose nor suggest to use a granulate comprising a fine filer fraction to obtain the improved mortar of the present invention.
Examples of suitable material of which the inorganic grains may consist are silicon oxide-containing and calcium carbonate-containing materials such as, for example, fly ash, quartz, blast furnace slags, limestone and sand. Preference is given to the use of sand or limestone.
Examples of water-soluble polymers which can be used are poly(vinyl alcohol), poly(acrylic acid), poly(methacrylic acid), poly(vinyl acetate), copolymers containing monomer units of vinyl alcohol, acrylic acid, maleic anhydride and vinyl acetate cellulose, and also salts of the above-mentioned polymers and copolymers.
Preferably, the grains of the fine fraction have a diameter <250 &mgr;m, more preferably <130 &mgr;m.
As a result the granular material is, for example, very suitable for use in the preparation of concrete which has a high compression strength and low water penetration.
A granular material employed in the method according to the invention preferably disintegrates very rapidly in water. Were the granular material to retain its consistency over a very long period during the preparation process of the concrete mortar, after the granular material has been added and been blended into the mixture of water and other components, this would unnecessarily delay the preparation process. Preferably, the granular material disintegrates within 600 seconds in water of 23° C., more preferably within 300 seconds, even more preferably within 60 seconds.
Even more preferably, a granular material used in the method according to the invention disintegrates so quickly in water that the granular material is first mixed completely and homogeneously through the mortar, before the granular material disintegrates. As a result, a highly homogeneous mortar is obtained which contains no agglomerates of the fine fraction or only very few of them. Additionally, this provides a very rapid mixing process.
The speed with which the granular material disintegrates can be influenced, for example, by the choice of the water-soluble polymer, the diameter of the granular material and the amount of water-soluble polymer contained in the granular material, based on the fine fraction of inorganic grains.
Very good results are obtained if the granular material has still not disintegrated after 2 seconds, more preferably after 5 seconds, even more preferably after 10 seconds in water of 23° C. The time after which the granular material has disintegrated in water is determined by 95 grams of water at 23° C. in a glass beaker having a volume of 250 ml and a diameter of 66 mm being stirred with a cylindrical magnetic stirrer having a diameter of 8 mm and a length of 40 mm, the stirrer speed being 625 revolutions per minute, 5 grams of the granular material being added to the water and the time then being determined at which the granular material has completely disintegrated.
Preference is given to the use, in the method according to the invention, of a granular material which has a strength of at least 30 N, preferably at least 40 N, even more preferably at least 50 N. Since such a granular material readily withstands forces which, for example, are exerted on the granular material during storage, transportation and during the addition, it is ensured that the granular material in the process retains its consistency well and does not suffer from crumbling or attrition, which again may give rise to the problems which manifest themselves during the use of a fine fraction which is not in the form of the granular material.
The strength of the granular material is determined by a granule being positioned between two parallel planar plates, the plates being moved towards one another in the direction perpendicular to the plates until the granule yields, the force being measured which has to be exerted on the plates, this being carried out for 10 grains from the granular material composition, and the average of the 10 measured forces being calculated.
Preference is given to the use, in the method according to the invention, of a granular material in which the water-soluble polymer used is the salt of a polymer which contains monomer units of styrene and of maleic anhydride (SMA polymer). Such a granular material has a beneficial dissolution rate and good strength. Preference is given to the use of the sodium salt or potassium salt of the SMA polymer. The salt of the SMA polymer can be prepared in a simple manner by the polymer, preferably as a powder, being combined, for example at a temperature of 20-150° C. and a pressure of 1-10 bar, with a solution of sodium hydroxide or potassium hydroxide and the mixture thus obtained then being stirred until the polymer in the form of the salt has dissolved.
The SMA polymer can be prepared with the aid of one of the known methods as described, for example, in Hanson and Zimmerman, Ind. Eng. Chem. Vol. 49, No. 11 (1957), pp. 1803-1807.
The SMA polyme
Courage Antonius J. F. M.
Friederichs Joseph P.
DSM N.V.
Marcantoni Paul
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