Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Reexamination Certificate
2000-05-16
2002-01-22
Cooney, Jr., John M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
C222S206000, C222S630000, C425S00400R, C521S142000, C521S146000, C521S149000, C521S155000
Reexamination Certificate
active
06340715
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a pressurized container for providing insulating foams including a foamable composition adapted for delivery from the pressurized container, for producing stable insulating foams, on the basis of an aqueous plastic dispersion. The composition is more particularly suitable for the production of insulating foams for constructional purposes.
2. Description of the Related Art
The composition of the invention serves for the production of insulating foams, which are more especially employed for thermal and humidity-proofing insulation by caulking or filling cavities. The principal applications are in the constructional industry, but also in the form of industrially employed products, for example for caulking cavities to avoid spaces likely to collect condensed water. Furthermore this composition may be utilized for the production of seals, as for example sealing tapes.
It is more especially in the construction sector that polyurethane foams are employed on an extensive scale, which are produced and worked by delivery of a prepolymer composition from pressure containers, as for instance aerosol cans, with the aid of propellants on site with a bulk weight of 10 to 100 g/l. So-called single component foams are moisture curing, that is to say same consist of a component able to react with atmospheric humidity, namely isocyanate groups. Dual component foams contain a reaction partner in the form of a second component so that curing to yield the finished foam does now not depend, or does not solely depend, on the presence of atmospheric humidity. Here as well the reactive first component comprises isocyanate groups, which react with the hydroxy or amine group present in the second component.
The prepolymers containing isocyanate groups utilized for the production of conventional polyurethane foams possess a special suitability for the production of stable foams but have one substantial disadvantage, namely the toxicity of the isocyanate containing components. This renders necessary the application of special precautionary measures for the filling and processing and for the disposal of residues. On the other hand installed PUR foams possess excellent insulating properties, they are not toxic and have good processing properties.
Compositions, which contain polyurethane prepolymers, are highly water-reactive. For this reason systems, which contain such prepolymers, can not be produced on an aqueous basis. Other liquid components, solvents and/or liquid additives, must consequently be used as vehicles for the foam forming components. For the selection of the vehicle components rigid limits are imposed owing to the reactivity of the isocyanate groups. Seen in this light it would be desirable to make foam forming polymers available able to be foamed from an aqueous dispersions.
The U.S. Pat. No. 3,912,666 discloses formulations of film forming polymers together with blowing gases for the production of foam pads. The formulation disclosed here has a non-ionic foam stabilizer added to it. The foam is described as being non-tacky, this being consistent with the use for cleaning purpose named.
The U.S. Pat. No. 4,036,673 describes a method for the production of adhesive foams with the aid of blowing gases from an aqueous dispersion, which collapses after its formation.
Furthermore several plastic dispersions are on the market, which together with blowing gas are held in a pressure package and which after delivery and foaming provide a stable foam in a short time. The product is conceived as a “tire patch”; the foam spreads over the wall of the tire, collapses as a film and seals off punctures. Such a formulation is for instance described in the U.S. Pat. No. 4,501,825.
The film forming mechanism is well described in the literature, see “Water borne Coatings” by K. Dören et al., Hansa Publishers, Munich, 1994. It is furthermore a known practice to control film formation by additives, such as associative thickeners, film formation adjuvants, fillers and the like, more particularly with a view to optimizing properties, for example in the case of products in the paint and coatings industry, see “Wässrige Polymerdispersionen, Syntheseeigenschaften—Anwendung” by D. Distler, Wiley-VCH Publishers, 1999. The production of foams and the theory of foam stabilization is also well documented in the literature and more particularly also the production of aqueous foams, see “Handbook of Aerosol Technology”, pages 358 ff and “Aqueous Aerosol Films”, P. A. Sanders, Krieger Publishing, Florida 1979.
Latex foams have been described in various connections for pressure can applications. The patent publication WO-A-98/12 248 describes foamable compositions for delivery from pressure cans in the form of stable foams, which consist of an aqueous emulsion of a film forming polymer, a liquid blowing agent and a solid, lipophilic and non-ionic surfactant with a HLB value of approximately 3 through 8 and possibly further additives. The patent publication WO-A-98/12 247 describes a foamable composition for pressure can delivery, which contains an aqueous emulsion, a film forming polymer, a liquid blowing agent, a solid, wax-like foam stabilizer and a liquid lipophilic surfactant.
It has been shown that while the foamable compositions described in the two last mentioned publications provide a stable foam immediately after delivery, this foam collapses in the course of time and does not do justice to the requirement to be met by a satisfactory insulating foam on a long term basis. The pronounced tendency to shrink may admittedly be mitigated by the systematic selection of non-ionic surfactants as foam stabilizers, but it may not be completely overcome. Moreover, the presence of non-ionic surfactants leads to the instability of the resulting foams when affected by humidity, as for instance under conditions of high atmospheric moisture.
However there is a need for a small celled, elastic, non-shrinking foam.
SUMMARY OF THE INVENTION
The present invention provides a small celled, elastic, non-shrinking foam produced with the aid of a conventional blowing mixture from an aqueous dispersion of a film forming plastic. More particularly there is a requirement for such a polyurethane foam.
This aim is to be attained with a composition, which comprises an aqueous dispersion of at least one film forming plastic with a content of 30 to 80% by weight of the film forming plastic, a blowing gas in an amount equal to 3 to 25% of the weight of the total composition, and one or more anionic foam stabilizers in an amount equal to 0.3 to 6% of the total composition.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The composition in accordance with the invention for the delivery of foams from pressure packages differs from the compositions in accordance with the prior art by the presence, more particularly, of an anionic foam stabilizer in a quantity of between 0.3 and 6% by weight. A fine-celled, elastic and substantially dimensionally stable foam is produced, which also behaves in an essentially inert manner toward the influences of humidity.
In addition to their foam stabilizing effect the anionic foam stabilizers employed in accordance with the invention perform a further function, namely the integration of the blowing gases in the aqueous phase. The model is the formation of an oil-in-water emulsion, i. e. the low molecular blowing gases are emulsified in the aqueous medium. It is assumed that for the formation of emulsified blowing gases in the aqueous phase in addition to the dispersed polymer particles furthermore emulsified blowing gas spherules are present.
The principal function of the stabilizers is guaranteeing foam stability during the film forming process and during drying. Anionic, water soluble foam stabilizers or, respectively, surfactants are generally suitable which, after foam formation caused by the blowing gas, form Langmuir films at the interface of the continuous aqueous phase with the disperse gas phase. Surprisingly, the stabilizing effect of
Cooney Jr. John M.
Rather AG
Reed Smith Hazel & Thomas LLP
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