Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Reexamination Certificate
2000-06-08
2002-07-02
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...
C521S133000, C521S138000, C521S155000, C521S159000, C521S174000
Reexamination Certificate
active
06414045
ABSTRACT:
FIELD OF INVENTION
The present invention relates to a one-component polyurethane foam composition, which contains at least one prepolymer (isocyanate prepolymer), which has isocyanate groups, at least one blowing agent and known auxiliary and additive materials, with improved embrittlement-free curing even at low temperatures and/or a slight ambient moisture content under the conditions given, and to the use of certain esters, free of reactive hydrogen atoms, as materials for improving the embrittlement-free curing of these one-component polyurethane foam compositions under the conditions given.
BACKGROUND INFORMATION AND PRIOR ART
The EP-A-O 480 342 discloses a one-component mixture for producing polyurethane foam for use from a pressure vessel. It contains an isocyanate group-containing prepolymer from a polyol and a polyisocyanate with a particular dynamic viscosity, conventional components and auxiliary materials, as well as 0.5 to 35.0% by weight of helium, neon, argon, nitrogen, oxygen, carbon dioxide, nitrous oxide or air as pre-foaming and blowing gas. Furthermore, it is stated that it may be advantageous to work with slight additions of low boiling solvents, such as esters, low-boiling esters, such as methyl acetate or ethyl acetate, ketones and fluorinated hydrocarbons, which reduce the viscosity.
The object of EP-A-O 200 801 is a one-component coating composition for producing protective coatings which, aside from an isocyanate prepolymer, contains plasticizer anti-settling agents, lamella-like extenders, color-producing pigments, moisture-binding agents and aliphatic esters. The aliphatic esters serve to extend the binder (pure solubilizer), to ensure the required processing viscosity and to attack the substrate, which is partially sensitive to the solvent, adequately yet not excessively. However, this state-of-the-art does not disclose one-component coating compositions, which contain a blowing agent and produce a polyurethane foam.
One-component polyurethane foams are used predominantly in the building sector, for example, for filling, insulating or fastening doors, windows and the like. Usually, for manufacturing these products, an isocyanate group-containing prepolymer (isocyanate prepolymer) is filled into a pressure vessel together with one or more blowing agents and conventional additives. The foaming prepolymer, brought out of the pressure vessel by the user, is cured under the action of the ambient moisture. At the same time, the reaction of the isocyanate groups, present in the prepolymer, with the water of the ambient moisture is used for the polymerization of the prepolymer.
Because the reaction partner, water, depends on the ambient conditions (temperature, humidity, air movement and like), such one-component polyurethane foam compositions react very sensitively to the absence of an adequate amount of the reactant, water. This problem arises particularly if the one-component polyurethane foam compositions in question are to be used at low temperatures. At low temperatures, the reaction rates naturally are slower and the moisture, available from the surroundings is less. Accordingly, it is usually recommended that the substrate, which is to be treated with the polyurethane foam composition, be moistened to begin with. However, this represents an additional step in the procedure for the user and affects the productivity. Moreover, at temperatures at or below freezing point, it is no longer possible to moisten the substrate because the temperature has dropped below the freezing point.
The visible indication of this effect of an insufficient availability of water is a slower, non-uniform or incomplete curing of the foam as well as a more or less pronounced embrittlement during the curing of the polyurethane foam. As a consequence, the incomplete curing of the foam can lead to a later expansion at higher temperatures and, associated therewith, to damage to the component.
The task of the present invention accordingly is to solve the problem of curing such one-component polyurethane foam compositions when less water is available, whether it be because of a lower humidity and/or because of low temperatures, so that an embrittlement-free, complete curing can be ensured even at low temperatures.
This task can be accomplished by adding to the one-component polyurethane foam composition certain esters, namely esters free of reactive hydrogen atoms, that is, free of hydroxy, mercapto, amino, imino and/or carboxyl groups, of a polycarboxylic C
2
to C
7
acid with a monohydric C
1
to C
7
alcohol and/or conversely a monocarboxylic C
1
to C
7
acid with a multihydric C
2
to C
7
alcohol.
Surprisingly, it has turned out that these esters, contained in the one-component polyurethane foam composition, react very easily with water or ambient moisture even at low temperatures and, in so doing, decompose into several molecules with reactive groups, that is, groups, which react with the isocyanate groups of the isocyanate, such as hydroxy groups, carboxyhydrol groups or NH groups. Because of the reaction of the ester with water and the use of polycarboxylic acids or multihydric alcohols, more reactive groups are available after the reaction than before. These reactive groups can then react directly with the isocyanate groups of the isocyanate prepolymer. It has turned out that the esters, which are preferably used pursuant to the invention, react so strongly with water, that the reaction between water and isocyanate, which otherwise is customary, is avoided during the curing of the one-component polyurethane foam composition and a direct reaction with the reactive reaction products of the esters used is achieved.
OBJECT OF THE INVENTION
The one-component polyurethane foam compositions of claim
1
are therefore the object of the present invention. The dependent claims relate to preferred embodiments of this inventive object, as well as to the use of the esters in question as means for improving the one-component polyurethane foam compositions containing the embrittlement-free curing.
SUMMARY OF THE INVENTION
The invention accordingly relates to a one-component polyurethane foam composition containing at least one isocyanate group-containing prepolymer (isocyanate prepolymer), at least one blowing agent and known auxiliary and additive materials, wherein at least one ester is contained, which is free of reactive hydrogen atoms and composed of a polycarboxylic C
2
to C
7
acid and a monohydric C
1
to C
7
alcohol and/or a monocarboxylic C
1
to C
7
acid and a multihydric C
2
to C
7
alcohol as a material for improving the complete and embrittlement-free curing even at low temperatures and/or when little moisture is available from the surroundings (low ambient humidity).
The ester, which is used pursuant to the invention and is free of reactive hydrogen atoms, is an ester, which is free of groups that react with the free isocyanate groups of the isocyanate prepolymer, that is, free of hydroxy, carboxyl or also amino groups.
Pursuant to a preferred embodiment of the invention, the polyurethane foam composition contains one or more esters of a saturated or unsaturated aliphatic C
2
to C
7
dicarboxylic acid with at least one C
1
to C
7
monoalcohol and/or at least one ester of a saturated or unsaturated aliphatic monocarboxylic C
1
to C
7
acid with at least one C
2
to C
7
polyalcohol, preferably a C
2
to C
7
dialcohol.
Esters, which are particularly preferred pursuant to the invention, are the esters of oxalic, malonic, succinic, glutaric, pimelic, suberic, citric, malic, maleic, fumaric, citraconic and mesaconic acid with at least one monohydric alcohol, such as methanol, ethanol, propanol, isopropanol, n-butanol, sec-butanol, t-butanol, pentaerythritol, pentanol, hexanol or heptanol or an ester of formic, acetic, propionic, butyric, isobutyric, valeric, isovaleric, pivalic, hexanoic or heptanoic acid with at least one multihydric alcohol, such as ethylene glycol, propylene glycol, butylene glycol, pentylene glycol, glycerol or pentaerythritol.
Especially prefer
Heimpel Franz
Huber Silvia
Vogel Peter
Cooney Jr. John M.
Hilti Aktiengesellschaft
Sidley Austin Brown & Wood LLP
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