JPH0187A - Boron nitride preceramic polymer - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

BACKGROUND OF THE INVENTION This invention relates to the synthesis of substituted borazines, the thermal polymerization of these borazines, and the ultimate conversion of preceramic borazine polymers to carbon-free boron nitride ceramics.

Ceramic materials, typified by boron nitride, have unique properties of great industrial importance.

However, due to their non-dissolving and non-melting properties, it is very difficult to process these materials into important end products. Bulk boron nitride is usually prepared by melting borax with ammonium chloride (
Tied, H., et al., Z.

Anorg, AI Igem, Chem, 147°p,
114 (1925)) or prepared by melting boric anhydride with urea in an ammonia atmosphere (
0° Connor, T,, J, Am, Chem, So
c, 84. p., 1753 (1952)). However, due to its non-melting and non-melting ceramic nature, the bulk material has not been useful in applying boron nitride as a paint to complex surfaces or forming it into complex shapes. For this purpose, soluble,
It is necessary to produce boron nitride directly from processable precursors. An important requirement for such precursors is that the boron nitride produced by their melting should not contain carbon or other troublesome impurities in the ceramic.

Borazine is potentially suitable as this type of boron nitride precursor because of its ability to produce soluble polymers upon heating. Preceramic polymers based on borazine, with neither boron nor nitrogen bound to carbon, are the most suitable for producing pure boron nitride fibers and coatings.

The polymerization of several substituted borazines has been reported in the literature. However, the mechanism of the reaction and the chemical structure and composition of the polymer are not clear, and therefore it is not always possible to predict the structure or composition of the synthetic product. Gerrard, W., et al., J.C.
hem, Soc,.

p., 113 (1962), the interaction of chloroborazine with the type of molecule represented by di-S-butylamine results in the formation of polymerized borazine rings bonded through cyclic boron and nitrogen atoms. However, it has been reported that the polymerization of B-tris(ethylamino)-N-triethylborazine by heating at 300°C for 4 hours results in polymerization into borazine rings bonded by ethyl-substituted nitrogen atoms. .

The method for producing polymers of borazine consisting of a repeating structure of boron-nitrogen bonds and the use of various alkylaminoborazines as starting materials are the subject of a Japanese patent (Japanese Patent No. 37°837 (1978)). Tanaguchi). However, in a careful replication of this method,
It was found that the pyrolysis products produced a polymer, boron nitride, which was impure due to the retention of carbon (Pacio
rek, ni, et al., J, of Polymer
Sci.

Sutaku, pp. 173-185 (1986)).

We have produced borazine polymers that can be ultimately converted to carbon-free boron nitride by synthesis of triamino-N-1 lis(trialkylsilyl)borazine and subsequent thermal condensation into preceramic polymers. Compositions and methods are described in U.S. Patent Section 4,581.468 (198
6). This polymer is called polymer A here.
That's what it means.

The main object of the invention is to provide a preceramic borazine polymer with a different structure from already patented materials which can also be converted pyrolytically into pure boron nitride. The polymer of this invention,
Here, it is called Polymer B.

Polymers A and B, which are soluble in organic solvents, can be used as precursors to allow the use of boron nitride ceramics that are applied in other ways that are impractical or impossible. After the preceramic polymer is in place, it can be converted under reaction conditions that remove substituents from the polymerized borazine ring to a pure boron nitride residue.

Easily processable polymers, such as those that can be converted to pure boron nitride ceramics by pyrolysis, can be converted into many useful physical forms, including fibers, shaped articles, coatings, foams, and (e.g., sintering aids). as a binder for ceramic particles, avoiding the use of additives (such as
It has the potential to produce ceramics.

Another main object of this invention is therefore to provide suitable preceramic polymers that can be dissolved in organic solvents and formed into solvent spun fibers or coatings.

It is also an object of this invention to provide a method for the conversion of pure boron nitride ceramics into preceramic polymers into fibers, coatings and shaped articles.

Other objects and advantages of this invention will become apparent to those skilled in the art in view of the accompanying disclosure.

SUMMARY OF THE INVENTION The present invention consists in the synthesis of preceramic polymers of the following general formula.

Here R is methyl, ethyl, propyl or butyl, and X is a positive integer.

In accordance with the objects of the present invention, there is now provided a new preceramic substituted borazine polymer having a structure and properties different from those already disclosed, but also capable of thermal conversion into pure boron nitride ceramics. Ru.

Also provided is a method of synthesizing this borazine polymer by reacting chloroborazine with disilazane.

Both reactants are dissolved in a mixture of organic solvents having at least one aromatic component and at least one non-polar aliphatic component, and the reaction is carried out in the presence of an inert gas.

These reactants are heated at low temperatures between -78°C and 0°C.
The interaction is allowed for a period of 4 to 24 hours, after which the temperature is allowed to reach ambient temperature and the precipitated by-products are removed by filtration. The soluble polymer product is isolated by removing the solvent from the solution.

In a preferred embodiment, the reaction is carried out under an atmosphere of nitrogen, argon or helium or mixtures of these gases at or near atmospheric pressure. In a particularly preferred embodiment, the synthesis is carried out in an equal mixture of benzene and hexane under an atmosphere of nitrogen at a temperature of about 0-50°C to -30°C for a period of about 3 to 24 hours.

According to another object of the invention, there is provided a method of preparing boron nitride ceramics from substituted borazine polymer precursors, in which the borazine polymer precursor is heated under an ammonia gas atmosphere within a period of about 4 to 30 hours. 1000
The borazine polymer precursor is heated at a rate necessary to raise the temperature to .degree. The system can be cooled to temperatures intermediate between about 300°C and 400°C.

Ammonia gas is degassed from the system, the system is cooled to ambient temperature, and nitrogen or other inert gas is then fed to the system at atmospheric pressure. In a preferred embodiment,
The ammonia atmosphere in this system is 400 and 760
The atmospheric pressure is between mmHg.

A similar method for the preparation of boron nitride ceramics from substituted borazine polymer precursors is provided in which the substituted borazine polymer precursors are heated from about 50° C. for about 10 to 20 hours before being treated with ammonia gas. It is heated under an atmosphere of halide acid at a temperature of 60°C. Using this method, the ammonia gas treatment time required to convert Polymer A to boron nitride ceramics can be reduced by a factor of 10. In a particularly preferred embodiment of this method, the halide gas is approximately 10
Hydrogen chloride (HCu) exists under a pressure of 0 mmHg, and ammonia gas exists under a pressure of approximately 500 mmHg.

In preferred embodiments of both curing methods, the borazine rings in the borazine polymer are substituted with silylamino groups. In a particularly preferred embodiment of the halide acid gas method, the borazine polymer has the structure of Polymer A.

We have now found that from polymers A and B, fibers and shaped and coated articles can be made. Accordingly, in yet another embodiment of the invention, a system of at least one substituted borazine polymer is produced in the form of fibers by melting and drawing at a temperature below that at which the polymer converts to boron nitride. Substituted borazine polymers are provided. In a preferred embodiment, fibers are melt drawn from Polymer A, and in other preferred embodiments, fibers are melt drawn from Polymers A and B. In a particularly preferred embodiment, boron nitride ceramic fibers are made from a system of substituted borazine polymers A and B present in equal proportions.

According to yet another embodiment of the invention, there is provided a borazine polymer in the form of a shaped article prepared by a method of melt polymer casting or extrusion or polymer solution evaporation.

According to yet another embodiment of the invention, a method of coating an object with boron nitride comprises heating the object in a system to a temperature of about 1000° C. and cooling it to ambient temperature. By dipping it into a solution of substituted borazine polymer so that a polymer coating is applied and heating the polymer coating in the presence of ammonia gas at a temperature sufficient to convert the preceramic polymer to boron nitride. A method comprising curing steps is provided.

In a particularly preferred embodiment of this method, the substituted borazine polymer is dissolved in a non-polar organic solvent such as hexane. Ammonia gas is 500 m in the final heat conversion
Exists at a pressure of mHH.

Pure boron nitride objects with a preliminary step of drying the polymer-coated objects in an atmosphere of hydrogen halide gas after removing the objects from the polymer solution and before proceeding to the thermal conversion step. Further provided are similar coating methods.

In a particularly preferred embodiment of this method, the halide acid gas is HCfl under a pressure of about 100 mm Hg.

In a preferred embodiment of this coating method, the substituted borazine polymer has the general structure of Polymer A.

DETAILED DESCRIPTION OF THE INVENTION The substituted borazine polymers of this invention have the following general formula % 22 where R is methyl,
It is a lower alkyl group such as ethyl, propyl or butyl, and X is a positive integer.

Polymer B is chloroborazine (Laubengaye
r, A, et al. (195'5) J, Amer, C
hem, Soc, 77, pp, 3699-37
00) and disilazane.

<sl'F &white> The synthesis reaction of chloroborazine and disilazane is preferably carried out over a period of 4 to 24 hours, with cooling (e.g., at a temperature between -78 °C and 0 °C), to form the aliphatic/disilazane. It is carried out in an aromatic mixed solvent system in an inert gas atmosphere. This method is described in detail in Example 1.

This synthetic method consists of introducing a solution of chloroborazine dissolved in an aliphatic/aromatic solvent system into a disilazane dissolved in an aliphatic solvent. During the course of this reaction, a precipitate consisting of a high molecular weight polymer is formed. At the end of the reaction, the precipitate is filtered off and the desired product, the soluble silylamino-substituted borazine polymer, is isolated by removing the solvent from the filtrate.

The use of aromatic solvents is utilized to direct the chloroborazine into the reaction. Examples of this solvent include toluene and xylene, but benzene is preferred, and is used alone or in combination with a saturated aliphatic solvent. The disilazane is introduced into an aliphatic solvent of the type heptane or preferably hexane.

Using the same substituted disilazane as the reactant, the choice of solvent and temperature at which the reaction is carried out becomes an important determinant of the yield of soluble polymer and its average molecular weight.

Product polymers also include a range of oligomers. Different solvent systems give polymers with different molecular weight distributions.

With a single solvent system, the upper limit on the molecular weight of a useful product polymer is the solubility of the polymer in that system. If the molecular weight of the polymer is in excess of the solubility limit, the polymer will precipitate and will not dissolve irreversibly.

Temperature affects the yield of soluble polymer.

It was found that at the limit (room temperature) all produced polymers do not dissolve and do not melt.

The synthesis and properties of Polymer B are compared to those of Polymer A (disclosed in our US Pat. No. 4,581,468) of the general formula: X is a positive number such as 1.2.3 or 4 and R is lower alkyl such as methyl, ethyl, propyl or butyl.

(Engraving of the specifications of the Imperial Emperor (no changes to the contents) f)? It can be easily synthesized by the reaction of ammonia gas with B-trichloro-N-)lis(trialkylsilyl)borazine as described in No. 33. Substitution of chloride groups by amino groups gives heptamers which are easily condensed into doubly and singly cross-linked dimers and roughly condensed into polymeric forms.

This reaction is normally carried out at a temperature ranging from -78°C to 25°C. Reaction times range from 4 to 24 hours, but longer or shorter times can also be used. The reaction is carried out under an inert gas such as nitrogen, helium or argon. Typically, ammonia is used in an amount from 2 to 10 times in excess of that required by the stoichiometry of the reaction. The subsequent condensation to the preceramic polymer is
It is carried out at temperatures ranging from 0° C. to 300° C. for 8 to 250 hours in an inert gas such as nitrogen, helium or argon or under reduced pressure.

The invention also includes fabrication of boron nitride that can be made from polymers A and B and mixtures thereof, including fibers, coatings, and shaped articles.

The boron nitride coating can be applied to the article by dipping the article in liquefied borazine polymer and then curing the polymer coating to form boron nitride, as described in Example 5.

Borazine polymers can be spun or drawn into fibers by a variety of methods well known to those skilled in the art (J, Riley).

To obtain the final boron nitride articles such as woven fibers, the preceramic fibers are condensed. It is drawn from the melt of Polymer A. The preceramic fibers are then incubated in gaseous ammonia for periods ranging from 8 hours to 27 days at gradually increasing temperatures from 60°C to 1000°C.
By heating, it is converted into boron nitride fibers. This polymer can also be solution fiber spun.

B-trichloro-N-)lis(trimethylsilyl)borazine (trichloro-N-)lis(trimethylsilyl)borazine (20 mfL) in hexane (50 mfL) was added to liquid ammonia (20 mfL) in a 100 °C 3-day flask fitted with a dry ice condenser and addition funnel while passing nitrogen through it.
10.0 g, 24.98 mmol) was added over 1.6 hours. The addition was accompanied by the formation of a white precipitate. The mixture was then gradually warmed to room temperature. Filtration in an inert atmosphere gave 4.04 g (100% yield) of ammonium chloride. After removal of the solvent, crude B-triamino-N-)lis(trimethylsilyl)borazine (7.38 g, 86% yield) was obtained from the filtrate. some 6
．． 60g was distilled under reduced pressure at 135℃, and then from 75℃ to 87℃
By-product boiling in the range (1.05 g, yield 15.
9%) were removed as a result. Slightly liquid residue (4,
80 g) consisted of a two-to-one mixture of doubly crosslinked borazine dimers and tetramers.

Elemental analysis calculation value "14H5L43N12.8788S'4.67
'B, 14.08%; N, 28.88%, MW
, 815 actual measurement value 2 B, 13.48%; N, 2
To further achieve condensation of the 8.78%, MW, 820 preceramic polymer, the above mixture of dimers and tetramers was heat treated from 1,196°C to 260°C.

The preceramic polymer was a mixture of doubly crosslinked tetramers and octamers.

Elemental analysis calculation value "22H80, 87N2348B18817.3
3'B, 18.48%, N, 31.09%; M
W, 1051 actual measurement value: B, 18.01%, N,
29.39%: MW, 1010 Carbon contaminated boron nitride ceramics are unsuitable for many applications. Both polymers A and B can be converted to essentially pure boron nitride ceramics. This is due to the fact that the substituents on the borazine side chains efficiently release carbon under high temperature conditions and in the presence of ammonia gas, which is present during the final condensation of the polymer's borazine rings during the curing process. This is because it constitutes a leaving group. Ammonia is essential for carbon desorption in this process.

Desorption of carbon from Polymer B is demonstrated in Example 2 by thermally converting bulk polymer to bulk boron nitride.

Polymers A and B clearly differ in their physical properties of fusibility, ie their tendency to melt and coalesce. Synthesized polymer B has a relatively low melting temperature, whereas synthesized polymer A has a low melting point of approximately 90°C.

The melting point of Polymer A can be determined by gradually heating it to further condense the oligomers, thereby increasing the molecular weight.
can be increased. During this condensation process, the temperature gradually increases. This typically spans a period of 8 hours to 10 days and is from about 50<0>C to about 300<0>C under an inert gas atmosphere.

After such treatment, Polymer A has a temperature of about 120°C to 1
It can be processed at a temperature of 60°C and melted and drawn into fibers, spun or other forms.

The subsequent curing and conversion of processed Polymer A to boron nitride further involves gradual curing and conversion, preferably in an ammonia atmosphere, to about 1000° C. for 12 days as typically required in the case of fibers. It is necessary to heat it to

However, curing of Polymer A can be accelerated by pretreating the processed polymer fibers with heat in the presence of a hydrogen halide, such as a HC-containing gas, as described in Example 4.

This preliminary treatment renders the fiber infusible and hardens it to prevent it from softening during the curing process.

The time required to convert these HCu-treated fibers to boron nitride by heating to 1000° C. in the presence of ammonia is consequently reduced from 12 days to 12 hours.

Polymers A and B, alone or in combination, can be processed such that the boron nitride ceramics produced from them by thermal transformation can be adapted to many specific applications.

One method of processing these preceramic polymers is through the production of polymer fibers.

Preceramic polymer fibers are melt drawn from Polymer A at 90°C to 160°C and subsequently converted to boron nitride ceramic fibers by gradual heating from 60°C to 1000°C over 12 days in an ammonia atmosphere. converted. Gradual heating is preferred in order to more completely polymerize Polymer A by heating without softening and melting during curing.

Improved fibers could be produced by melting and drawing a mixture of Polymers A and B as described in Example 3. Both types of fibers were completely colorless, free of carbon, and did not melt or lose weight when heated to 1000° C. in nitrogen.

Combining Polymers A and B to melt and draw fibers of mixed composition offers several advantages. Polymer B works as an excellent filler because it is cheaper and shrinks less during conversion. However, more important is the fact that the presence of Polymer B imparts stiffness to the fibers in the early stages of conversion to boron nitride, which makes the process approximately 10 This allows the process to proceed at twice the speed.

Polymer fibers melt-drawn from a mixture of polymers A and B do not require condensation prior to fiber production or pretreatment prior to the curing process. This blend polymer fiber was produced in the presence of ammonia for only about 25 hours.
It is converted into nitride by heating to 00°C.

Times and temperatures stated above are bench scale □
It must be emphasized that it is about the process of It is anticipated that in manufacturing scale processes this process may be accelerated to a greater extent and much higher temperatures may be used.

Various other processes known in the art may also be suitable for processing borazine polymers into fibers (e.g. J, R11ey, Chapter X1: Single Fiber Spinning and Drawing in Polymer Processing'). ,C,5
Chi 1dknecht, ed., Interscience, New York, 1956).

In the spinning process, a fibrously shaped polymer, which is in a fluid state, is drawn under pressure through a number of orifices in a jet or spinneret and assumes a solid state in the form of fibers. The polymer may be melted or dissolved in a suitable solvent to bring it into a fluid state. Suitable solvents for these polymers include hexane, heptane, benzene, toluene, xylene and other inert organic solvents, as well as mixtures of these solvents.

In melt spinning, molten polymer emerges from a spinneret in the dimensions of fibers or filaments;
It is still in a liquid state. Its solidification is accelerated by an inert cold stream. The filament thus produced can be removed at a constant speed by a drive wheel and then taken up by a spool or bobbin.

In solution spinning, a polymer dissolved in a solvent is
It is spun into fibers or filaments by one of two methods: dry spinning or wet spinning. In dry spinning, dissolved polymer is extruded through a spinneret and
It emerges as a thin stream into a region where the thin stream is dimensionally stable and the solvent is removed quickly enough so that it does not stick or touch. By passing the stream through a heated cabinet with a circulating atmosphere of warm inert gas and with the vapor pressure of the solvent kept low enough so that the outside of the filament is not redissolved by excess solvent, The solvent can be removed. This process can be accelerated by diluting the original solvent with a more volatile non-solvent.

In wet solution spinning, solvent is removed from a stream of drawn filaments by passing it through a liquid bath known as a spin bath. The spin bath is
A non-solvent that quickly diffuses into the filament and causes precipitation or agglomeration may also be used.

The molten polymer can also be plasted with an inert gas through the melt bath, using attractive forces to pull the streamer out.
Spinning may be performed by shooting the melt together with an inert gas at high speed.

In all these steps, the borazine polymer
The fibers are placed under an atmosphere of inert gas or stored under an inert liquid until curing converts the fibers to boron nitride as described in Example 3. In any of the fiber conversion steps, it is useful to raise the temperature to about 1200° C. while drawing the fibers at the end of the step.

Boron nitride can be built into the desired shape by molding and casting borazine polymers before being cured in a variety of ways (see, for example, J. Manson, "Polymers" Vol. 10, pp.
, 634-35. McGraw-Hill Technology Encyclopedia, Volume 5 (1)
9g2)). Conventional techniques such as compression molding, injection molding, extrusion and casting etc. are believed to be applicable to the use of this polymer.

Each property of a polymer provides advantages in particular applications. The conversion step of polymer A in the presence of ammonia as already described is 1. It requires long staged heating cycles for further polymerization, thereby raising the initially low softening point of the polymer. At the same time, however, a low softening point is desirable for drawing and spinning fibers and filaments from the melt. The infusible nature of Polymer B allows it to be cured and converted to pure boron nitride in as little as 7 hours (Example 2), and the process described for coating alumina fibers or other fibers (Example 2). 5) is also important. If Polymer A were used alone to coat fibers, it would be soft and
It will produce a sticky coating and the fibers will clump together and become dull.

Each of the polymers A and B has their respective properties in fibers that can be derived from the mixture of polymers A and B without the need for precondensation or in the preparation of a preliminary H
This contributes to the fiber's ability to harden in 25 hours without Cu treatment.

One of the more useful applications of boron nitride ceramics is to provide a protective coating on materials to prevent chemical or physical changes. Boron nitride coatings prevent undesired interactions (such as chemical reactions or dissolution) between materials in other mutually incompatible states, such as the composite and the matrix in which it is embedded. can provide a barrier. It may also act as an electrical insulator or provide a thermal barrier, allowing the material to perform its function at temperatures where its integrity would not otherwise be maintained. becomes possible. The preceramic borazine polymers described herein are particularly well suited for such coating applications. The object to be coated is immersed in a polymer solution and then the polymer is thermally converted into a pure boron nitride coating by any of the methods described.

A special application is the coating of alumina fibers. Alumina fibers, which would otherwise dissolve, can be coated with boron nitride for use in glass. Example 5 provides a method of coating such fibers.

Boron nitride's coefficient of thermal expansion is low compared to many other materials, and the material also has high thermal stability, making boron nitride shaped articles useful in electronics applications such as internal combustion engine components. and other applications where these properties are important.

A more complete understanding of the invention can be obtained by reference to the examples described below, which are not, however, intended to unduly limit the invention.

Example 1 Preparation of Preceramic Polymer B Hexamethylenedisilazane (11.3 g, 70° 0 mmol in hexane (120 mm) while passing through nitrogen
) to a stirred solution of 1:1 benzene/hexane (25 m
Chloroborazine (2゜5g, 13.6mm) in (1)
A solution of o l) was added over a period of 1.5 hours at -50<0>C to -40<0>C. Following the addition, the solution was stirred at -35° C. for 1.5 hours. The reaction mixture was then gradually warmed to room temperature. 0.6 g of the formed precipitate was filtered and the filtrate was evaporated to obtain 2.3 g of preceramic polymer. This material is very soluble in hexane and
More than 480 mg dissolved in 660 mg of hexane.

Elemental analysis calculation value: C21H89N26B17Si7:C,23
,89,I(,8,42,N,34.20:B,LS,
23; S i , 18.45; MW, 1064.8
9 Actual measurement value: C, 23, 99, H, 8, 20; N
, 35.39°B, 14.8B, MW, 1100 Example 2 Preparation of bulk boron nitride 102.5 mg of preceramic polymer B was prepared in a platinum cup inserted into a quartz tube under 500 mm Hg of ammonia. , heated from 25°C to 990°C over 7 hours. The white residue is 37°6 mg, which is 6
This corresponds to a weight loss of 3.32%.

Calculated weight loss: C2, H89N26B, 5St7-15 8Nj15.
04%.

This material is completely colorless, carbon-free, and
There was no melting or any weight loss when heated in air at 000°C.

Example 3 Preparation of boron nitride fibers Preceramic fibers were melt drawn from a 1:1 mixture of polymers A and B. The fibers were converted to boron nitride fibers by gradual heating from 68°C to 970°C over 25 hours in an ammonia atmosphere.

The fibers produced in this way were completely colorless, free of carbon and did not melt or lose any weight when heated to 1000° C. in air or nitrogen.

Example 4 Preparation of boron nitride fibers: Preceramic fibers melted and drawn from preliminary Hut treated Polymer A were heated at 58° C. for 16 hours in a hydrogen chloride atmosphere at a pressure of 100 mmHg. The fibers treated in this way did not soften or melt up to 225°C. Next, this fiber was gradually heated from 50°C to 1000°C over 12.5 hours in an ammonia atmosphere of 50QmmHg. After cooling to 366°C, the system was evacuated and allowed to reach a temperature of 25°C - once and brought to atmospheric pressure with nitrogen.

Example 5 Alumina fiber coated with boron nitride Continuous polycrystalline alumina fiber yarn (E.

1. duPont de Memours an
A section of 200-filament (product of d Company) was heated gradually in a quartz tube in an air atmosphere from 25 DEG C. to 620 DEG C. over a period of 3 DEG 5 hours to remove any surface coating. The system was then placed under vacuum and the temperature was increased to 985° C. over a period of 3.25 hours. After the system was cooled to room temperature, nitrogen was introduced to bring it to atmospheric pressure. The heat-treated fibers were then immersed in a hexane solution containing 9.6% by weight of boron nitride preceramic polymer B under an inert atmosphere. Conversion of the preceramic polymer coating to pure boron nitride was accomplished by gradual heating from 100° C. to 977° C. over 8 hours in an ammonia atmosphere at 500 mm Hg. The system was cooled to room temperature under vacuum and brought to atmospheric pressure with nitrogen. All coating steps were performed twice.

In this way, alumina fibers coated with boron nitride ceramic were produced.

Modifications of this invention are possible that will be apparent to those skilled in the art in view of the above disclosure without departing from the concept and scope of this invention.

Patent applicant: Ultra Systems Defense and Space Q, Inc.

Claims (28)

[Claims] (1) A polymer represented by the following formula. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ Here, R is a methyl, ethyl, propyl, or butyl group of the general formula C_nH_2_n_+_1, and X is a positive integer. (2) A pentamer represented by the following formula. ▲Contains mathematical formulas, chemical formulas, tables, etc.▼ (3) The polymer of claim 1 in the form of fibers or filaments. (4) Claim 1 is in the form of fibers or filaments.
A mixture of the described polymer and a polymer of the formula: ▲Contains mathematical formulas, chemical formulas, tables, etc.▼ (5) The polymer of claim 1 in the form of a shaped article. (6) A polymer having the formula: in the form of a shaped article. ▲Contains mathematical formulas, chemical formulas, tables, etc.▼ (7) A mixture of the polymer of claim 1 and a polymer of the formula: in the form of a shaped article. ▲Contains mathematical formulas, chemical formulas, tables, etc.▼ (8) A mixture in which the polymer according to claim 4 and the polymer according to claim 7 are present in approximately equal proportions. (9) A method for preparing a polymer according to claim 1, comprising: (a) in a mixture of organic solvents having at least one aromatic component and at least one non-polar aliphatic component; reacting chloroborazine with disilazine under an atmosphere of active gas at a temperature below 0° C. but above the freezing point of said mixture for a period long enough to form a polymer solution; (b) precipitating from said polymer solution; (c) then isolating the polymer by removing the solvent from the polymer solution. 10. The method of claim 9, wherein the atmosphere comprises a gas or mixture of gases selected from nitrogen, helium, and argon. 11. The method of claim 10, wherein the gas or gas mixture is at atmospheric pressure. (12) about -50 to -3 in a solvent mixture containing equal parts of benzene and hexane for about 3 to about 24 hours.
10. The method according to claim 9, wherein chloroboracine and hexamethyldisilazine are reacted at a temperature of 0<0>C. (13) In a system having an ammonia gas atmosphere, the borazine polymer precursor is heated at a temperature of 4 to 24
A method of preparing a ceramic material from a borazine polymer according to claim 1, comprising the step of gradually heating at a rate necessary to increase the temperature to about 1000<0>C over a period of time. 14. The method of claim 13, wherein the ammonia atmosphere is at a pressure between about 400 mmHg and about 760 mmHg. (15) A method of preparing a boron nitride ceramic from a substituted borazine polymer, the method comprising: (a) heating the substituted borazine polymer at a temperature of at least 40° C. below the softening point of the polymer in an atmosphere of hydrogen halide; , to a softening temperature of the polymer; and (b) then heating the polymer under an ammonia atmosphere at a temperature sufficient to convert the polymer to boron nitride. (16) The method according to claim 16, wherein the hydrogen halide gas is hydrogen chloride. (17) The hydrogen halide gas is approximately 100 mm
17. The method of claim 16, wherein the method is under pressure of Hg. (18) The ammonia gas is about 400 to 76
16. The method of claim 15, wherein the method is under a pressure of 0 mmHg. (19) A method of coating an object with boron nitride, the method comprising: (a) coating the object with a substituted borazine polymer in a solution of a substituted borazine polymer in a solvent for the substituted borazine polymer or in a melt of the polymer; immersing the object in an atmosphere of gas inert to the polymer to be coated; (b) removing the object coated with the polymer from the solution; (c) soaking the object coated with the polymer in an atmosphere of ammonia gas The method comprises the steps of heating below to convert the polymer coating to boron nitride. 20. The method of claim 19, further comprising repeating steps (a) to (c) to coat the object with multiple layers of boron nitride. 21. The method of claim 19, wherein the substituted borazine polymer in the soaking step is in the form of a solution, and the solvent for the polymer is hexane or heptane. (22) The method of claim 19, wherein the ammonia gas in step (c) is at a pressure of approximately 500 mmHg. (23) After removing the object from the solution in step (b) and before proceeding to step (c), the method further comprises heating the polymer-coated object in an atmosphere of a halide acid. 20. The method of claim 19, comprising: (24) The method according to claim 19, wherein the hydrogen halide gas is hydrogen chloride. (25) The method of claim 19, wherein the hydrogen halide gas is under a pressure of approximately 100 mmHg. (26) The substituted borazine polymer has the following formula:
Single and doubly crosslinked fused B-triamino-N-
20. A method according to claim 19, which is tris(trialkylsilyl)borazine as well as mixtures thereof. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ Here, R is methyl, ethyl, propyl, or butyl of the general formula C_nH_2_n_+_1, and x is a positive integer. (27) The method according to claim 19 or 23, wherein the borazine polymer is substituted with a silylamino group. (28) The method of claim 26, wherein the borazine polymer is the polymer of claim 1.