Compositions: coating or plastic – Coating or plastic compositions – Inorganic settable ingredient containing
Reexamination Certificate
2000-12-12
2003-05-20
Wood, Elizabeth D. (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Inorganic settable ingredient containing
C106S725000, C106S727000, C106S808000, C106S809000, C106S810000, C106S728000, C106S781000
Reexamination Certificate
active
06565645
ABSTRACT:
The present invention relates to a hydraulically setting composition comprising specific auxiliaries, a process for preparing such a composition, the use of particular compounds as auxiliaries and the use of a composition according to the invention for producing shaped bodies and for specific building compositions, plasters and renders and knifing fillers.
Calcium sulfate as anhydrite or hemihydrate has long been, because of its ability to set on reaction with water (hydraulically), a valued raw material having many interesting properties, for example low shrinkage, a refractory nature and pH neutrality during curing. Furthermore, large amounts of gypsum are nowadays obtained from flue gas desulfurization and should be used in an environmentally friendly manner.
However, a disadvantage of set gypsum mortar, screeds and coatings is, for example, the relatively low water resistance of these systems. The exterior use of gypsum, for example as render, is a still unsolved problem today.
It is already known that gypsum can be waterproofed by means of specific hydrophobic polysiloxanes which are added in amounts of up to 2% by weight. However, this is disadvantageous in that the addition of polysiloxanes during production causes great environmental pollution due to their nonbiodegradability and their unfavorable ecobalance. In addition, the quality of gypsum products modified in this way is not satisfactory for external applications.
WO 97/08112 describes CaSO
4
-containing compositions which comprise fatty additives for waterproofing, control of setting times, rheology, the water retention capability and elastification. The publication mentions many fats which are suitable for hydrophobicizing gypsum, including ester betaines. The amount used is disclosed as from 0.1 to 30% by weight.
DE-A 196 32 152 describes a process for producing insulation boards based on mineral and paper fibers. Here, mineral fibers, binders and customary additives are slurried in water, an insulation board is formed by application of the slurry to a screen and the insulation board is dried and consolidated. The publication describes the possibility of using, for example, betaines as surface-active additives, which improves dewatering and has a significant waterproofing effect on the surface of the dried insulation boards. Use of betaines for reducing the water penetration depth in hydraulically setting compositions is not described.
EP-A 0 787 698 discloses a composition comprising cement and a surfactant. It describes, inter alia, the use of amidopropylbetaine as foam stabilizer in foamed gypsum compositions. An improvement in the water resistance is not described in this publication.
Hydraulically setting compositions should not only have a good water resistance but also meet further requirements which have been able to be met only partially, if at all, by the compositions known hitherto. Furthermore, certain desirable properties often have to be abandoned in the case of the compositions known hitherto if another property is to meet particular requirements.
Thus, for example, the known waterproofing agents often lead to a deterioration in the handlability of the waterproofed compositions which are often difficult to introduce into water. The effect of the waterproofing agents in respect of the water resistance of the set compositions (shaped bodies) frequently leaves something to be desired. In general, large amounts of waterproofing agents have to be added in order to achieve satisfactory water resistance of the shaped bodies. However, the addition of water-proofing agents frequently leads to a drastic increase in the setting time, which cannot be justified by the only slight improvement in the water resistance. The addition of large amounts of waterproofing agents can also lead to a deterioration in the materials properties of the shaped bodies, which is undesirable. Moreover, the addition of waterproofing agents often leads to thickening of a mix of composition and water, i.e. the amount of a hydraulically setting, inorganic compound which can be mixed with water to achieve a consistency necessary for processing is less than would be the case for a comparable composition without waterproofing agent. This leads to increased pore volumes and thus generally to a higher water absorption capacity, as result of which the desired waterproofing effect is weakened and the water resistance of the shaped bodies is impaired. The addition of commercial fluidizers (for example sulfonated melamine-form-aldehyde condensates) does generally lead to a reduction in the pore volume, but does not achieve a satisfactory reduction in the water absorption capacity.
In the present context, the term “pore volume” refers to the volume of the voids formed when the composition sets without additional introduction of air (i.e. without foam formation). The pore volume thus has a critical effect on the density and thus on the weight and the mechanical properties of the cured composition. Applications in which a high mechanical strength is necessary therefore generally require a cured composition having a low pore volume. Applications in which low weight is important correspondingly require larger pore volumes. However, in all the applications mentioned, there is a need for a low water absorption capacity of the cured shaped body. Hydraulically curing compositions having different pore volumes and unchanged, low water absorption capacity would therefore be desirable.
Users of such hydraulically setting compositions often wish, for example, to give the set composition a coarse-pored appearance. This effect can be achieved, for example, by addition of surfactants to the composition, leading to foam formation during stirring and thus formation of a porous structure. However, customary surfactants are frequently sensitive to calcium ions and form water-insoluble soaps which cannot contribute to foam formation. Furthermore, the addition of surfactants is often associated with an increased water absorption capability of the cured composition. (The term “coarse-pored” refers in the present context to generally approximately spherical pores which have been formed by introduction of air bubbles into the still fluid mixture of composition and water). There is therefore a need for compositions which allow production of coarse-pored shaped bodies which have a low water absorption capacity.
It is therefore an object of the present invention to provide a hydraulically setting composition which leads to sufficiently water-resistant solids without use of waterproofing agents. A further object of the invention is to provide a hydraulically setting composition which leads to solids having an unchanged, low water absorption capability at different pore volumes. It is also an object of the present invention to provide a hydraulically setting composition which makes it possible to produce coarse-pored shaped bodies which have a low water absorption capacity.
For the purposes of the present invention, a low water absorption capacity means a water absorption rate of not more than about 1 ml/(24 h*cm
2
), as measured using a KARSTEN tube at a water column height of 15 cm.
It has now been found that hydraulically setting compositions which comprise auxiliaries in the form of at least largely water-soluble, ionic or aqueously ionizable compounds containing a carboxyl group and, in the &bgr; position relative to the carboxyl group, a polyether group (ether carboxylic acids) or a quaternary amino group (alkyl and amido betaines) do not have the disadvantages known from the prior art.
In particular, it has been found that hydraulically binding compositions comprising auxiliaries of the abovementioned type display low water absorption, display only a slight decrease in compressive strength after storage in water and redrying (compared to the initial compressive strength) and have a constantly low water absorption rate at different pore volumes. It has also been found that the proportion of auxiliaries is lower compared to conventional waterproofing agents known fr
Fandel Thomas
Klauck Wolfgang
Klein Johann
Sattler Hans-Peter
Schilling Gaby
Harper Stephen D.
Henkel Kommanditgesellschaft auf Aktien
Ortiz Daniel S.
Wood Elizabeth D.
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