Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Reexamination Certificate
1999-11-15
2002-06-11
Foelak, Morton (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
C521S135000
Reexamination Certificate
active
06403669
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to thermostable alveolar materials, a process for synthesis of these materials and the uses of these materials, in particular in the field of petroleum drilling and in all of the fields where it is desirable to have alveolar materials that have good fire resistance and that procure good sound and thermal insulation. These alveolar materials are sometimes referred to as foam materials, cellular materials or expanded materials.
BACKGROUND OF THE INVENTION
A large number of documents describe rigid or flexible cellular materials that have good thermal resistance and fire resistance properties, as well as various methods for production of these products. One of the oldest production techniques of alveolar materials with a polyimide base, described, i.a., in U.S. Pat. No. 3,249,561 and U.S. Pat. No. 3,883,452 in the name of Du Pont de Nemours, consists in producing a polyimide foam from a polyamide-acid solution in the presence of an agent that decomposes during heating, which makes possible the formation of polyimide by releasing a gas such as carbon dioxide or carbon monoxide. This process is relatively difficult to use since the starting polymer is in dilute solution in a polar organic solvent, and it is necessary to control simultaneously the evaporation of the solvent, the imidation reaction and the formation of the cellular structure. With the thermoplastic polyimides such as the polyetherimides, sold by the General Electric Plastics Company under the trade name ULTEM®, the addition of a porophoric agent (sometimes also referred to as pore-forming) has also been used to create the cellular structure, as is described in, for example, U.S. Pat. No. 4,532,263 in the name of Mobil Oil. Another method, described in, for example, U.S. Pat. No. 4,007,922 in the name of the Upjohn Company, consists in mixing this type of polyimide with hollow microspheres.
A method that was the subject of a very large number of publications consists in synthesizing the polyimides by reacting an aromatic bis(ortho-acid-ester), instead of an aromatic dianhydride, on a diamine or on a mixture of several diamines. This reaction provides, by heating to a high temperature, polyimides with release of a water molecule and an alcohol molecule for each imide cycle that is formed. These two volatile compounds are used as porophoric agents in the production of the cellular materials of polyimides. Since the quantity of volatile products released is relatively large, the reaction is generally conducted in two stages. A first partial polycondensation stage is carried out in solution to form imide oligomers, which are isolated in powder form by precipitation in a non-solvent medium. This meltable power that is optionally mixed with various additives is placed in a mold and heated above its melting point. The expansion of the material is brought about by the continuation of the polycondensation reaction.
This production technique has been used with numerous monomer mixtures. It is possible to cite, by way of illustrative example of this method, U.S. Pat. No. 3,502,712, in which is described the reaction of a diester of benzophenone-tetracarboxylic-3,3′,4,4′acid with metaphenylenediamine. The use of a diamine mixture, for forming more flexible polyimide foams, that comprises aromatic diamines and flexible diamines such as acrylonitrile-butadiene-diamines is described in, for example, U.S. Pat. No. 4,456,862 or the diamino-poly(dimethylsiloxanes) in U.S. Pat. No. 4,535,099.
The various methods that are set forth above make it possible to produce thermostable polyimide foams that have very varied characteristics. They can be rigid, semi-flexible or flexible according to the nature of the monomers or polymers that are used to prepare them. They generally have open pores, but in some cases, the pores can be closed, and they cover a quite wide range of density and resistance to compression.
In a general way, however, most of these production processes require a strict monitoring of the synthesis conditions of polymers and the operating protocol of these polymers to obtain reproducible results.
The problems that are encountered for the preparation of the alveolar polyimide materials are also found again for the preparation of most of the thermostable, thermoplastic alveolar materials that are obtained from thermoplastic polymers that have a high glass transition temperature. In particular, the obtaining of alveolar materials by raising the temperature, which is a method that is a priori very simple, is made delicate and its application is difficult because the operating temperature of the initial polymer for obtaining the mixture that makes possible the subsequent obtaining of the foam material is high (often 300 to 400° C.) and often much higher than the triggering temperature of the porophoric agent (often 150 to 250° C.).
SUMMARY OF THE INVENTION
This invention relates to the alveolar materials that maintain the main properties of the thermostable alveolar materials of the prior art, but whose use is made less difficult by the use of modified thermostable polymer mixtures whose operating temperatures for obtaining alveolar materials, in particular by increasing temperature, are on the order of the triggering temperature of the porophoric agent or relatively close to this triggering threshold.
DETAILED DESCRIPTION OF THE INVENTION
The alveolar materials of this invention are defined as being characterized in that they comprise at least one thermostable, thermoplastic polymer, at least one epoxide resin that is modified by at least one aromatic polyamine and at least one pore-forming agent or the degradation product(s) of said pore-forming agent.
Within the meaning of this description, any thermoplastic polymer that has adequate mechanical properties to be able to be used also at a temperature that is greater than 150° C. is referred to by the term thermostable, thermoplastic polymer. This definition is the one that is commonly accepted by ones skilled in the art and incorporated into, for example, the basic work that constitutes the encyclopedia Ulmann's Encyclopedia of Industrial Chemistry (see Volume A21, page 449) of the fifth edition published in 1992).
The alveolar materials of this invention contain at least one thermostable, thermoplastic polymer, preferably amorphous, most often selected from the group that is formed by the polyetherimides (PEI), the polysulfones (PSU), in particular the polyethersulfones (PES) and the polyphenylene-sulfones (PPS), and the polyphenylene-ethers (PPE). These alveolar materials contain at least one epoxide resin that is modified by at least one aromatic polyamine, whereby said resin is usually formed from at least one polyepoxide that contains in its molecule at least two epoxide groups and at least one aromatic, preferably occupied polyamine that most often comprises in its molecule at least two primary amino groups, whereby the molar ratio of the polyamine to the epoxide is most often such that from 1.6 to 2.6 epoxide groups correspond to each amino group. Most often, the aromatic polyamine that is used comprises at least one alkyl substituent that has 1 to 12 carbon atoms that are located in alpha-position of one of the amino groups.
The polyetherimides that are used for producing the alveolar materials according to this invention are most often selected from the group of polyetherimides (PEI) that are sold on the market and in particular from among the products that are marketed by the General Electric Plastics Company under the name ULTEM®. The term polysulfone can produce ambiguity. Actually, the first polymer of commercial significance whose base group contains a sulfone group—SO
2
—is the polymer that is marketed by the AMOCO Company under the name UDEL®. This particular polysulfone thus often receives the generic name of polysulfone. Within the meaning of the description, the term polysulfone covers the generic meaning and does not have only the limiting meaning of the UDEL®-type polysulfone. The polysulfones th
Bonnet Anthony
Camberlin Yves
Grenier Jacky
Pascault Jean-Pierre
Sautereau Henri
Foelak Morton
Institut Francais du Pe'trole
Millen White Zelano & Branigan P.C.
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