Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Patent
1992-06-23
1994-04-12
Welsh, Maurice J.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
521172, 528 49, C08G 1814
Patent
active
053026268
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is concerned with polyurethane materials and relates to the use of reaction mixtures containing polyester polyols as polyol component in the production of solid polyurethane materials by casting.
Solid polyurethane materials produced by casting are widely known in the prior art. They generally consist of the so-called "casting resin", a compound containing at least two isocyanate group and a polyol component ("hardener"). Mixing of the polyol component with the casting resin containing isocyanate groups produces a reaction mixture which, optionally after the introduction of desired additives, is cast into a mold where it is able to cure during the polyaddition reaction to form polyurethane polymers. A review of polyurethane casting systems can be found, for example, in E. W. Becker and D. Braun "Kunststoffhandbuch", Vol. 7, Polyurethanes, Verlag-Hanser, 1983 or in B. A. Dombrow, "Polyurethanes", 2nd Edition, New York (1965).
Above all, there is a need for polyol components which may be derived from renewable raw materials. Some time ago, the natural product, castor oil, was used as hydroxyl component in the production of polyurethane materials ("Plastics Laboratory"--Princetown University, "Castor Oil Polyurethanes and Applications as Potting Components", U.S.O.T., pages 99 to 165). The low viscosity of castor oil proved to be an advantage by providing for easy processing during the production of the polyurethane materials. Polyurethane materials obtained using castor oil now no longer satisfy present-day requirements in regard to tensile strength, hardness, resistance to thermal deformation and electrical properties.
2. Discussion of Related Art
Accordingly, it is proposed in DE-OS 36 30 264 and European patent application 0 125 579 to use ring-opening products of epoxidized triglyceride oils with monohydric lower alcohols instead of castor oil as the polyol component. However, polyurethane materials based on polyether polyols show a greater tendency towards inflammability and a pronounced tendency towards hydrophilicity. In particular, the tendency towards hydrophilicity leads to increased bubble formation during the processing and/or storage of the polyurethane materials in the presence of atmospheric moisture, so that product quality is reduced.
Improved flameproof behavior and greater stability to hydrolysis is observed in the case of polyurethane materials based on polyester polyols.
U.S. Pat. Nos. 2,882,249 and 4,025,477 relate to polyurethane materials of which the polyester polyol component has been produced by ring-opening of epoxidized soybean oil with ricinoleic acid (U.S. Pat. No. 2,882,249) or with acrylic acid (U.S. Pat. No. 4,025,477). In both patent specifications, the polyurethane materials are produced by reaction of the isocyanate component with the polyester polyols either with heating or in the presence of an organic solvent. However, relatively high temperatures are undesirable in the production of polyurethane materials because polyurethanes have the characteristic of reversion i.e. back reaction of the urethane bonds to the starting materials. In addition, the use of organic solvents is both ecologically and economically questionable and should therefore be avoided.
In the production of polyurethane materials, the problem of inadequate compatibility of the isocyanate component with the polyol component often arises, so that unwanted separation and clouding can occur in the final polyurethane material. In addition, the production of polyurethane materials requires starting materials of low viscosity so that production and processing can be carried out in the absence of bubble formation.
Accordingly, the problem addressed by the present invention was to enable isocyanate-compatible polyester polyols of low viscosity to be used as polyol component in the production of polyurethane materials by casting. Using polyester polyols such as these, polyurethane materials would even be able to be produced without havi
REFERENCES:
patent: 4025477 (1977-05-01), Borden et al.
Daute Peter
Gruetzmacher Roland
Hoefer Rainer
Stoll Gerhard
Grandmaison Real J.
Henkel Kommanditgesellschaft auf Aktien
Jaeschke Wayne C.
Szoke Ernest G.
Welsh Maurice J.
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