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
2002-11-06
2004-03-23
Wu, David W. (Department: 1713)
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...
C524S560000, C524S555000, C524S562000, C524S577000, C428S510000, C428S514000, C428S521000, C428S522000
Reexamination Certificate
active
06710118
ABSTRACT:
BACKGROUND OF THE INVENTION
Field Of The Invention
The present invention relates to an aqueous polymer dispersion whose polymer, present in disperse distribution, is composed in free-radically polymerized form of
from 20 to 65% by weight of at least one vinylaromatic monomer (monomers A),
from 30 to 75% by weight of at least one monomer having two conjugated, ethylenically unsaturated double bonds (monomers B), and
from 0.5 to 10% by weight of at least one other monomer, C, selected from the group consisting of &agr;,&bgr;-monoethylenically unsaturated mono- and dicarboxylic acids and amide or ester derivatives thereof
and whose alkali metal ion content GA, based on the mass of the dispersed polymer, is ≧0.5% by weight, the pH of the aqueous dispersion medium being adjusted to a value below 6.
Description Of The Background
The present invention further relates to the use of the aqueous polymer dispersion as a water-vapor barrier, and also for coating substrates or the walls of damp rooms and refrigeration rooms. The present invention additionally extends to a process for preparing the aqueous polymer dispersion and also to aqueous polymer formulations comprising the aqueous polymer dispersions.
Air normally contains a certain amount of water vapor which exerts a defined partial pressure. This water vapor uptake by the air is limited and depends on the temperature. As the temperature rises, there is a great increase in the water vapor uptake capacity. At the maximum amount of vapor, the partial pressure is equal to the saturation pressure of water at the same temperature. The percentage ratio of the amount of vapor present in the air to the maximum possible amount is termed relative atmospheric humidity. Given a constant absolute moisture content, the relative atmospheric humidity falls as the temperature rises and, conversely, rises on cooling. On going below the dew point temperature the amount of vapor present in excess of the saturation level condenses to form dew.
Where, for example, a porous wall separates two areas having different partial pressures of air and water vapor, then molecules of water vapor or, respectively, air pass through this wall until the concentrations or pressures are equal. If the wall at the same time has a temperature gradient along its thickness, the saturation pressure of water may be exceeded within the wall and there may as a result be formation of dew which damages the wall (eg. reduction in its thermal insulating effect, development of molds, etc.). Against this background it is desirable, for example, to make the interior walls of damp rooms (the term damp rooms as used herein refers to rooms whose atmosphere has an increased water-vapor content relative to the atmosphere of their surroundings; examples of damp rooms are kitchens, bathrooms, dairy rooms, industrial rooms, cellar rooms) as impermeable as possible to water vapor, ie. to provide them with a water-vapor barrier. Similar comments apply to the exterior walls of rooms whose surrounding atmosphere has a relatively increased water-vapor content (eg. the exterior walls of refrigeration rooms). A further area of application for water-vapor barriers is constituted by wood coatings. Owing to its hygroscopic nature, wood shrinks or swells in accordance with changing relative atmospheric humidity, as a consequence of the uptake or release of water to which this change in humidity gives rise; the wood warps, which is generally accompanied by damage to the coating on the wood. It is therefore desirable either to give the wood surface a water-vapor impermeable finish before applying the actual protective coating, or to make the wood coating itself impermeable to water vapor.
From Römpps Chemie-Lexikon, eighth edition, 1981, Cm-G, Franck Verlag, Stuttgart p. 974 it is known that the aqueous Diofan® polymer dispersions of BASF AG are able to form films having high impermeability to water vapor. Accordingly, films of Diofan A 601 and of Diofan A 690 are very suitable as water-vapor barriers both for typical wall surface materials, such as cement slurry coats, concrete, plaster, plasterboard, wood particleboard or chipboard, plywood, hardboard and masonry, and for wood itself.
In this context the water-vapor barrier effect can be obtained in a simple manner by coating the respective surface either with the aqueous polymer dispersion itself or with an appropriate composition containing the aqueous polymer dispersion as binder. When the coating dries, the polymer film exerting the barrier effect is formed.
The abovementioned Diofan grades are able to form films of enhanced elasticity even at the most common application temperatures (from 5 to 35° C.). This is important insofar as the substrates which are to be given a water-vapor impermeable finish generally have cracks whose expansion is subject to fluctuations in the case of temperature change. Owing to their enhanced elasticity, the Diofan films are able to follow these fluctuations in an advantageous manner without themselves cracking (crack sites open up the passage of water vapor) and thus to form a long-term barrier to water vapor.
A notable feature is that the Diofans are able to transfer the abovementioned profile of properties even to coating compositions which in addition to the Diofan comprise up to 60% of their overall volume solids content of added, finely divided mineral materials, such as fillers and pigments (while fillers and pigments are normally distinguished from one another on the basis of their different degrees of fine division and of their different refractive index, the term pigment as used herein should be interpreted here as including both; correspondingly, the volume proportion mentioned above forms the pigment volume concentration (PVC)). This opens up the possibility of giving the water-vapor barriers visual appeal and of producing them, in a simple manner, with variable coat thicknesses.
The Diofan films also have an outstanding capacity for adhering to the materials mentioned as possibilities for wall surfaces.
A disadvantage of the Diofans, however, is that the vinylidene chloride which they contain in polymerized form is subject to progressive hydrolysis over time under the action of the aqueous dispersion medium, in the course of which hydrolysis hydrogen chloride is formed. The latter is an unwanted contaminant and has an adverse effect, inter alia, on the stability on storage and the thickening and formulation properties of corresponding coating formulations (for example, finely divided CaCO
3
pigment is attacked by the evolution of hydrogen chloride).
EP-A 773245 discloses aqueous polymer dispersions which are highly suitable, inter alia, as water-vapor barriers for sealing walls in damp rooms. That laid-open specification maintains that the alkali metal content (GA) should be ≦0.5% by weight, based on the mass of the dispersed polymer. According to the teaching of EP-A 773 245, the effect of the polymer dispersion as a water-vapor barrier would be lost at higher alkali metal ion contents. In order to stabilize the polymer dispersion adequately for its use as a water-vapor barrier, its pH is raised to more than 6. In accordance with EP-A 773 245 this is done by using ammonia as the neutralizing agent instead of metal hydroxides. In certain applications, however, especially in enclosed spaces, this leads to odor nuisance when the polymer dispersion is applied to the substrate.
SUMMARY OF THE INVENTION
It is an object of the present invention to remedy the disadvantages depicted and to provide an aqueous polymer dispersion for use for producing water-vapor barriers which can be applied to the substrate in particular without odor nuisance and which at the same time has the advantageous profile of properties of the Diofans.
We have found that this object is achieved in that aqueous polymer dispersions whose polymer, present in disperse distribution, is composed in free-radically polymerized form of
from 20 to 65% by weight of at least one vinylaromatic monomer (monomers A),
from 30 to 75% by weight of at l
Anselmann Thomas
Koppers Markus
Schmidt Marco
Schmidt-Thümmes Jürgen
Wistuba Eckehardt
Sastri Satya
Wu David W.
LandOfFree
Aqueous polymer dispersion and its use as a water-vapor barrier does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Aqueous polymer dispersion and its use as a water-vapor barrier, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Aqueous polymer dispersion and its use as a water-vapor barrier will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3269490