Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Patent
1995-08-15
1998-10-20
Cooney, Jr., John M.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
521172, 521173, 521174, C08J 900, G08G 1808
Patent
active
058247130
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a foamable two-component material based on polyurethane, which can be used, for example, to produce freely foamed seals on a surface or in a groove. Furthermore, the invention relates to specific individual components of this material as well as to objects made of such a material.
Polyurethane foam seals, which are produced in situ at the place where they are used, from their components, by the free expansion of the polyurethane material, have been known for a long time (compare DE 15 94 266 C3, DE-OS 18 08 821). With this technique--as also in the production of other polyurethane foams--expansion takes place at the same time as the chain lengthening reaction; the expanded structure is so-to-speak fixed as a consequence of the polymer build-up and cross-linking reactions. In principle, the following can be considered as components for producing the foam: such that the properties of the finished products can be varied very greatly by means of the structure of the components and their chain length; (NCO groups), which can react with the Zerewitinoff-active H atoms of component A; especially preferred are poly-isocyanates based on 4,4'-diphenyl-methane-di-isocyanate (MDI).
Previously, the expansion was generally effected by physical means, but for some time the trend has increasingly been to let the gas needed for the expansion be generated in situ by a chemical reaction. In this way, the fluoro-chloro-hydrocarbons, which are ecologically objectionable because they destroy ozone, could be replaced by carbon dioxide, which is much less damaging. With FIPM systems (Foam In Place Materials, in situ foamed materials) this has in the meantime also become the state of the art. Products are known which can be foamed in grooves due to their low viscosity, as well as products which can be foamed freely on variously shaped surfaces due to their thixotropic properties. The components are processed by means of mixing and dosing systems; the mixing process itself takes place in dynamic or static mixing chambers.
The free surface of materials foamed in this way is formed by an integral skin. With hardnesses above about 50 Shore A units, they generally have material strength properties which are certainly sufficient for their purpose; in most cases, this also applies to the notch impact strength and tearing strength of the integral skin. However, the softer the material, the less is the mechanical strength of the integral skin. Until now, no material was known, which could be produced by the described methods, and which, with Shore A hardnesses less than 5, would have a similar or comparable elongation on rupture as materials with Shore A hardnesses in the range of 40. The tear propagation strength of the known FIPM systems is generally low and unsatisfactory.
It is therefore an object of the invention to specify a foamable, two-component material of the type mentioned in the introduction, which makes it possible to produce foamed products with a high elongation on rupture and with a good tear propagation strength, even in conjunction with low hardness.
Another object of the invention is to furnish special individual components, pre-polymers, and the like, for such a two-component material.
It is also an object of the invention to specify foamed materials of this type, with an integral skin that has especially high mechanical strength and tearing strength.
The characteristics of the independent claims serve to achieve this object, while the dependent claims define the preferred embodiments. An essential aspect of the inventive solution is the feature of forming a two-component material of the type in question, such that one component (A) is a polymer which essentially has only two hydroxyl groups per molecule, and the other component (B) is an isocyanate component which likewise is essentially bi-functional. Customary other additives can be provided as necessary.
Without intending to be bound to a particular theory, the invention assumes, when choosing suitable components for the inventive foamable
REFERENCES:
patent: 4412013 (1983-10-01), Chang
G. Oertel; Kunststoff Handbuch, Polyurethane, 2. Auflage, Bd. 7 (1983) p. 79.
G. Oertel; Kunststoff Handbuch, Polyurethane, 2. Auflage Bd. 7 (1983) pp. 76, 77.
Horeis Kai
Razzak Ramzi
Schmitz Franz Peter
Cooney Jr. John M.
H.B. Fuller Licensing & Financing Inc.
Quan Nancy N.
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