Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Reexamination Certificate
2002-06-18
2004-03-16
Cooney, John (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
C138S118100, C138S141000, C138S145000, C428S425800, C521S054000, C521S099000, C521S124000, C521S126000, C521S127000, C521S137000, C521S174000, C523S218000, C523S219000
Reexamination Certificate
active
06706776
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to syntactic foams, a process for the preparation of these syntactic foams, pipes insulated with these syntactic foams, and a process for the production of these pipes insulated with syntactic foams.
Rigid foams and processes for their production are well known in the art. Such foams are typically produced by reacting a polyisocyanate with an isocyanate reactive material such as polyol in the presence of a blowing agent. A lot of the blowing agents used in the past are no longer acceptable, and the ones developed in recent years are available at much higher costs. Furthermore, the state of the art rigid foams prepared with blowing agents do not exhibit the high compression set required when foams are used, i.e. in applications like deep sea pipeline insulation.
In recent years, the substantial increases in costs of the basic materials used to make foam, has encouraged the development and use of filler materials to reduce the amount of the basic materials used and the weight of the finished materials. One of the suggested filler materials and insulating materials utilizes hollow microspheres.
The expression “syntactic” as used herein refers to the use of hollow spheres in a polymer matrix to produce a cellular material.
Expanded microspheres consisting of a synthetic thermoplastic resin shell that encapsulates a liquid blowing agent are known. See, for example, U.S. Pat. Nos. 4,829,094, 4,843,104 and 4,902,722. U.S. Pat. Nos. 4,829,094 and 4,843,104 disclose a syntactic-polymer foam composition having a low density filler containing free flowing microspheres.
U.S. Pat. No. 4,916,173 discloses a polyurethane syntactic foam compositions for millable modeling stock applications. These PU syntactic foam compositions have high glass transition temperatures and low coefficients of thermal expansion, and are prepared from a polymeric isocyanate, an amine-based polyol, a polyether triol, molecular sieve material and hollow microspheres. The foams are described as a solid polymer matrix. These compositions are based on polymethylene poly(phenyl isocyanate) and result in low physical properties (i.e. tensile strength, elongation, etc.) which may be suitable for modeling stock applications, but not for the more demanding requirements in deep sea pipeline insulation
A solid polymer matrix is disclosed by U.S. Pat. No. 4,959,395. This patent describes bulk polymerization of cycloolefin monomers by ring-opening polymerization wherein the microencapsulated blowing agents aid in filling molds during RIM procedures such that both surfaces of the article being molded remain in contact with the mold surfaces.
U.S. Pat. Nos. 4,303,729 and 4,303,736 disclose the use of hollow plastic microspheres as filler materials in plastics. The microspheres described by these two are generally large diameter microspheres, i.e. in the range of 200 to 10,000 microns. These microspheres can be made from low heat conductivity plastic compositions and blown with a low heat conductivity gas to make improved insulation materials and composites.
Hollow microspheres having lower loadings of 2 to 5% by weight of the total composition are disclosed by U.S. Pat. No. 4,038,238. Low density polyurethanes are produced from rapid-setting polyurethane-forming compositions containing light weight hollow spheres or microballoons and a liquid viscosity reducing agent.
A rigid syntactic foam comprising glass microballoons is disclosed by U.S. Pat. No. 4,082,702. These foams are obtained by mixing an organic polyol, a polyisocyanate, a catalyst for the reaction of the polyol and the polyisocyanate, microballoons, and a flame retardant foam having a bimodal cell structure.
U.S. Pat. No. 3,510,392 discloses glass nodules in cellular polyurethane. The polyurethane comprises a polyol and/or polyester reacted with an polyisocyanate, and water during crosslinking to provide a gaseous blowing agent. The reactive components are homogeneously mixed in a suitable mixing device with a surfactant and catalyst to control the rate of reaction. Cellulate glass nodules are added to the homogeneous mixture in the bottom of a mold cavity which is then closed and foaming occurs. These are suitable for building panels having a continuous polyurethane phase and a discontinuous phase (i.e. cellular glass nodules).
Syntactic rigid PUR/PIR foam boardstock is described by U.S. Pat. No. 6,166,109. These hollow microspheres are filled with a hydrocarbon, air or vacuum, to introduce uniform cell geometries in the foams. The microspheres, which have an average diameter of 0.01 to 60 microns, are encapsulated with a closed cell polyurethane foam. Foams in the examples are based on a polyester, a surfactant, catalysts, water, a chlorofluorocarbon blowing agent and a polymethylene poly(phenylisocyanate). These syntactic rigid foams have a bimodal cell structure.
The JP 4257429 reference describes the manufacture of foam sheets with smooth surfaces which are useful for thermal insulators, packaging materials, etc. The foam sheets of this reference can be prepared by applying a composition containing an organic polymer binder and a low boiling point solvent sealed thermally expandable microcapsules on a base film, laminating a polyester film on the coated layer, heating to dry and expand the coated layer and removing the polyester film. The resultant foam sheets have uniform closed cells and a smooth surface.
Thermally insulating syntactic foam compositions are disclosed by U.S. Pat. No. 6,284,809. These foam compositions have thermal conductivities less than 0.120 watts/meter-° K and exhibit acceptable strength and buoyancy characteristics for subsea applications at depths of up to about 10,000 ft. These syntactic foams are formed from 40-45 volume % of a resin binder containing hollow microspheres which comprise between about 55 and about 60 volume % microspheres and between about 65 and 50 volume % minispheres. Microspheres are described as having a diameter between 1 and 100 microns, and minispheres are defined as having diameters from ⅛ inch up to ⅜ inch.
It has now been found that a syntactic foam can be prepared having long potlife (i.e. 4 minutes) and short demolding times (i.e. less than 10 minutes), excellent hydrolytic stability combined with low water absorption and very good physical properties, i.e. high elongation combined with high tensile strength at microsphere filler levels of 10-70%. The syntactic foams of the present invention require a polyurethane composition comprising (1) a liquid diphenylmethane diisocyanate, (2) an isocyanate-reactive compound comprising a blend of one or more low unsaturation difunctional polyoxypropylene polyethers, one or more polyoxypropylene polyethers wherein the starter comprises at least one nitrogen atom, and one or more polyoxypropylene polyethers wherein the starter comprises an organic compound having at least three hydroxyl groups, and, optionally, one or more low molecular weight diols and/or triols, (3) a filler having a density of less than 1 g/cm
3
, and (4) at least one organo-metallic catalyst.
SUMMARY OF THE INVENTION
This invention relates to syntactic foams, to a process for the preparation of these syntactic foams, to pipes insulated with these syntactic foams, and to a process for the production of pipes insulated with these syntactic foams.
Syntactic foams of the present invention comprise the reaction product of:
(1) a liquid diphenylmethane diisocyanate having an NCO group content of from about 10 to about 33.6%, preferably 15 to 32% and most preferably 20 to 30%, and a viscosity from about 10 to about 5,000 mPa·s at 25° C., preferably 10 to 3,000, and most preferably 10 to 1,000 mPa·s at 25° C.; with
(2) an isocyanate-reactive component comprising:
(a) at least 10% by weight (preferably from 10 to 30% and most preferably from 10 to 20%) by weight of one or more polyether polyols having a functionality of about 2 to about 4, preferably about 3, a (number average) molecular weight of 200 to about 8,000, preferably between 240 and 4
Guether Ralf
Markusch Peter H.
Sekelik Tom L.
Bayer Corporation
Brown N. Denise
Cooney John
Gil Joseph C.
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