Compositions: coating or plastic – Coating or plastic compositions – Inorganic settable ingredient containing
Reexamination Certificate
2000-07-17
2002-06-18
Berman, Susan W. (Department: 1711)
Compositions: coating or plastic
Coating or plastic compositions
Inorganic settable ingredient containing
C106S724000, C106S726000, C106S713000, C106S728000, C106S729000, C106S730000, C106S733000, C106S737000, C106S738000, C106S739000, C106S741000, C106S746000, C522S081000, C522S083000, C522S084000, C522S086000, C522S088000
Reexamination Certificate
active
06406536
ABSTRACT:
SCOPE OF INVENTION
The present invention regards the use of organic additives useful for the preparation of cementitious compositions having the improved property of maintaining the luminance and quantity of colour unaltered for a longer period of time after being laid or applied.
TECHNICAL PROBLEM
One of the important uses of cement (whether grey cement or white cement) is for the preparation of mortars for plasters.
Generally, plaster consists of three layers: a bottom layer, referred to as the scratch coat, which must stick to a cementitious substrate, whether compact or very porous; a second layer, referred to as the floated coat; and a third layer, referred to as the finishing coat, which must be more resistant according to the conditions of exposure.
The composition of the plaster, in particular white plaster, must meet the need to obtain, in addition to good mechanical strength and durability over time, also surfaces with good appearance, and consequently uniform as regards colour and texture.
The constancy of colour of white cement may cover, obviously within certain limits, the variations in the colour of the sand.
In actual fact, however, perhaps on account of the progressive increase in pollutants present in a typical metropolitan environment, the surface protection of these products remains resistant in big towns for increasingly shorter lengths of time, with a consequent degradation of the product from the point of view of appearance.
There is thus particularly felt the need to solve the problem of maintaining the original appearance of the surface of plasters for as long as possible.
STATE OF THE ART
The applicant previously reported in WO98/05601 filed on Jul. 24, 1997 that this problem may be effectively solved by using cementitious compositions comprising in mass particles of appropriate photocatalysts capable of oxidizing, in the presence of light, oxygen and water, the pollutant substances present in the environment.
One type of photocatalyst useful for this purpose, i.e., capable of oxidizing, in the presence of light, air and ambient humidity (oxygen and water), the pollutant substances that come into contact with the surface of the hydraulic binder (or the corresponding mortars and concretes) in the hardened state, is in particular titanium dioxide, or one of its precursors, preferably prevalently in the form of anatase, possibly doped with atoms other than Ti.
The presence of titanium dioxide and organic additives renders the application of cementitious compositions, for example plaster compositions, problematical, especially if this application is made using a roller, a brush or a paint sprayer. In addition, titanium dioxide can decompose organic additives. It is therefore by no means unimportant to choose and/or dose the organic additives that are suitable for obtaining good characteristics of film coating and texture, in particular of plasters.
SUMMARY
The applicant has now found a combination of additives that is particularly advantageous for the preparation of cementitious compositions that can ensure a high conservation of the degree of white, which contain in mass a photocatalyst that is able to oxidize, in the presence of light, air and ambient humidity, the pollutant substances present in the environment, and that enables cementitious compositions to be obtained which are particularly suitable for being applied by brush, sprayer or roller.
The essential organic additives for cementitious compositions according to the present invention are the following:
a) at least one melamine resin, obtained via condensation of melamine with formaldehyde;
b) at least one cellulose ether;
c′) at least one polymer chosen from among an ethylene polymer, an acrylic polymer, and a terpolymer comprising as co-monomers at least one ester of acrylic acid with an alcohol and at least one ester of vinyl alcohol with a carboxylic acid; or alternatively to c′)
c″) a latex chosen from among an acrylic latex, a styrene latex, and a butadiene latex;
d) at least one chemically modified starch.
The organic additives selected according to the present invention may be mixed, at the moment of use, with the other components of the cementitious composition, or else, according to a typical embodiment of the present invention, may be in the form of a pre-formed homogeneous mixture obtained by mixing together the various organic additives, possibly pre-ground down to the desired fineness, possibly in the presence of one or more other additives and/or additional components of the cementitious composition, using conventional methods and equipment.
In this case, the mixture of organic additives according to the present invention comprises the components a), b), c′) and d); or else, when the component c″) is used instead of c′), the components a), b) and d) alone, in so far as c″) is added to the cementitious mixture at the moment of its preparation.
Consequently, the subjects of the present invention are the following: the use of the aforesaid organic additives, in combination with one another, for the preparation of cementitious compositions comprising the above-mentioned photocatalyst; the mixture of additives a), b), c′) and d) and the mixture of additives a), b) and d) as defined above, characterized in that they comprise the aforementioned photocatalyst; the dry premixes comprising the additives a), b), c′) and d), or the additives a), b) and d) as defined above, characterized in that they comprise the above-mentioned photocatalyst; and the cementitious compositions containing the aforesaid photocatalyst, characterized in that they comprise the above-mentioned additives from a) to d), the cementitious products obtained from them, and the corresponding processes for their preparation.
DETAILED DESCRIPTION
In the present text, by “binder” or “hydraulic binder” is meant a pulverized material in the solid, dry state, which, when mixed with water, yields plastic mixtures that are able to set and harden, for example a cement.
By “dry premix” is meant a homogeneous mixture suitable for being mixed with water and yielding cementitious compositions (for example, mortars and concretes), comprising at least one cement binder, one or more additives for cementitious compositions, and possibly one or more inert materials.
By “cementitious composition” or “cementitious mixture” is meant a composition in which a binder is mixed with water, and possibly with aggregates of varying grain size. The cementitious compositions thus comprise both cement pastes, i.e., mixtures comprising binder and water, without aggregates, and conglomerates, i.e., mixtures comprising, water, binder and aggregates.
The “aggregates” or “inert materials” may be coarse aggregates, such as crushed stones or gravel, or fine aggregates, such as sand, and are classified in the UNI 8520 Standards.
Examples of conglomerates are mortars (mixtures comprising binder, water and fine aggregate) and concretes (mixtures comprising water, binder, fine aggregate and coarse aggregate).
The clinker used for the preparation of a binder for the present invention is any clinker of portland cement as defined in the UNI ENV 197.1 Standard, i.e., a hydraulic material made up of at least two thirds by weight of calcium silicates (3CaO SiO
2
) and (2CaO SiO
2
), the remaining part being Al
2
O
3
, Fe
2
O
3
and other oxides.
In the broad definition of “hydraulic binder” according to the present invention are included both cements (white, grey or pigmented) defined according to the aforementioned standard UNI ENV 197.1, as well as the so-called “cements for debris dams”, the cementitious binding materials, and hydraulic limes, as defined in the Act No. 595 of May 26, 1965.
According to the present invention, the dry premix or the cementitious compositions obtained therefrom may thus contain white, grey or pigmented cement, preferably white cement.
The particular characteristic that essentially distinguishes white cement from the other cements is precisely that of being perfectly white. The typical
Caśsar Luigi
Pepe Carmine
Berman Susan W.
Hedman & Costigan ,P.C.
Italcementi S.p.A.
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