JP3074041B2 - Organic amide modified polysilazane ceramic precursor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001] The present invention relates to silazane polymers. Silicon nitride is of great interest as a ceramic material because of its high thermal and oxidative stability and high hardness. In addition, it has the advantages of low electrical conductivity, low thermal expansion, excellent thermal shock and creep resistance, high strength at high temperatures, and excellent wear resistance. One method of producing ceramic materials containing silicon nitride is the thermal decomposition of organic polysilazane. See, for example, U.S. Pat. No. 4,482,669.
Discloses crosslinking in the presence of a basic catalyst such as an alkali metal amide of an ammonolysis product of an organodihalosilane. This material is particularly useful as a binder for ceramic powders. In general, conventional methods for producing polysilazane ceramic precursors have the disadvantage that it is difficult or impossible to adjust the viscosity of the polysilazanes to a suitable viscosity for the intended use. For example, low viscosity is desirable for thin film or permeable porous ceramic substrate applications, and high viscosity is desirable for making fibers.

[0002] The present invention relates to a process for preparing silazane polymers by ammonolysis of organohalosilanes, a mixture of (1) ammonia or ammonia and a substituted or unsubstituted alkyl or aryl amines of 1-4 carbon atoms, RSiX ₃ RR′SiX ₂ and mixtures thereof, wherein X is Cl, Br or I, and R and R ′ are the same or different and are hydrogen, substituted or unsubstituted carbon atoms A group selected from alkyl having 1 to 6 carbon atoms, aryl, alkenyl having 2 to 6 carbon atoms and alkynyl group having 2 to 6 carbon atoms,

With at least one kind of Si—H
Producing a silazane ammonolysis product containing a silicon halide compound having a bond; 2) combining the silazane ammonolysis product with 0.1 to 30% by weight of an organic amide or thioamide based on the weight of the ammonolysis product. A step of mixing; and 3) a step of heating from 30 ° C. to 300 ° C.

[0004] The viscosity of these polymers can be easily adjusted and adjusted to the desired viscosity for the end use of the polymer.

Further, according to the present invention, a polymer in which at least one of R and R 'is an alkenyl or alkynyl group can be cured by applying energy to generate a free radical.

[0006] In the first step of the manufacturing method according to the present invention, mixtures of one or more compounds having the structural formula RSiX ₃ or RR'SiX ₂ can be used. Optionally, RR '
R "SiX, SiX ₄ or. The reaction mixture mixtures thereof can be present in the reaction product of at least one, S
It must contain a silicon halide compound having an iH bond. The halogenated silicon compound suitable for the production method according to the present invention includes, for example, methyldichlorosilane, vinylmethyldichlorosilane, tetrachlorosilane, tetrabromosilane, trichlorosilane, vinyltrichlorosilane, methyltrichlorosilanephenyltrichlorosilane, ethyltrichlorosilane , Propyltrichlorosilane, butyltrichlorosilane, methyltribromosilane, dimethyldichlorosilane, phenylmethyldichlorosilane, dimethyldibromosilane, trimethylchlorosilane, dimethylchlorosilane, dimethylvinylchlorosilane, and trimethylbromosilane.

[0007] The silazane ammonolysis product is Si-H
It is formed to include a bond. When only ammonia reacts with the silicon halide compound, the main product of ammonolysis is a mixture of cyclic compounds of various ring sizes, but may also contain small amounts (usually less than 1%) of linear products. . When a mixture of ammonia and an alkyl or aryl amine is used, the ammonolysis product contains more linear products than cyclic compounds.

[0008] The ammonolysis product is mixed with from 0.1 to 30% of an organic amide or thioamide, based on the weight of the ammonolysis product. Preferably, 0.5 to 5
% By weight of the amide or thioamide are mixed. After addition of the organic amide or thioamide, the mixture is heated to 30 to 300 ° C, preferably 110 to 180 ° C,
Partially cross-linked, increasing molecular weight and viscosity, i.e., the viscosity is between 15 and 20,000 cps (mP
a) and hydrogen gas is released. The reaction is performed in the presence or absence of a solvent, but is preferably performed in the absence of a solvent. Although the exact reaction mechanism is not known, the first step in the reaction is to cleave the bond between the nitrogen and hydrogen atoms and the C = O or C = S bond of the amide or thioamide. It is believed that hydrogen gas is generated by being inserted between nitrogen and silicon atoms. If no Si-H bonds are present in the ammonolysis product, there is no cross-linked structure and therefore no evolution of hydrogen gas.

The silazane polymer formed is a common organic
Soluble in organic solvents, and in the absence of moisture,
It can be a liquid that is stable. Alternatively, the solid
It can be formed by reaction with high concentrations of amide at high temperatures. this
These solids are generally not stable in common organic solvents. Departure
Organic amides and thios used in the method of Ming
Amides are monofunctional or polyfunctional, substituted or unsubstituted.
Alkyl or aryl of 2 to 6 carbons, alkenyl of 2 to 6 carbons
Or an alkynyl compound of 2 to 6 carbons
You. Suitable organic amides and thioamides are e.g.
Amide, N-methylacetamide, N, N-dimethyla
Cetamide, benzamide, thiobenzamide, formamide, N-methylformamide, dimethylformamide, urea, N- methylurea, 1,1-dimethylurea,
Includes 1,3-dimethylurea and 1-methyl-2-thiourea.

[0010] The viscosity of the final product can be controlled by varying the amount of organic amide or thioamide that is reacted with the silaza ammonolysis product. Low concentrations of the reactants produce low viscosity polymers, while high concentrations of the reactants produce extremely viscous polymers or solids. Its viscosity is also affected by the heating temperature, i.e. higher temperatures produce higher viscosities.

The silazane polymer of the present invention containing at least one alkenyl or alkynyl group is further crosslinked or cured through the alkenyl or alkenyl group by supplying energy to generate free radicals. For example, the polymer can be heated in the presence of a radical source such as a peroxide. When a liquid polymer is heated in the presence of a peroxide, a solid polysilazane is formed. The polymer can also be crosslinked by exposing it to UV light or electron beam radiation.

The cured or uncured polysilazane of the present invention can be pyrolyzed at a temperature of at least 800 ° C. under an inert atmosphere or an atmosphere containing ammonia.

The silazane polymer can be used to produce ceramic fibers and foams, penetrate the preform construct and subsequently pyrolyze to form a composite silicon nitride-containing structure.
It can be used for the production of oxidation-resistant coatings, as thin films for electrolysis, as adhesives or sealants, as binders for ceramic or metal powders and in injection molding.

In the following examples, all reactions are performed in nitrogen. The solid amide is recrystallized from dry ethanol before use and then stored in a desiccator. Liquid amides are available from Perrin and Armarego
"Purification of Labor
The amide was distilled and stored in nitrogen. The liquid amide was added by syringe for reaction of the ammonolysis product with the organic amide. The solid amide is added to the sparged flask under a strong nitrogen flow.

Example 1 A vinyl-substituted silazane ammonolysis product is produced as follows. A three-necked flask containing 5 liters is equipped with an overhead mechanical stirrer, a dry ice / acetone condenser (-78
° C), ammonia / nitrogen inlet tube and thermometer. The apparatus was sparged with nitrogen and then hexane (1760 milliliters), (dried over 4A molecular sieve), methyldichlorosilane (20
9 ml, 230.9 g, 2.0 mol) and vinylmethyldichlorosilane (64 ml, 69.6)
g, 0.5 mol). The ammonia is added at a rate of 3.5 l / min (9.37 mol) for 1 hour. During the addition, the reaction temperature increases from 25 ° C to 69 ° C. After 1 hour, the ammonia flow was stopped and the reaction mixture was cooled to room temperature. The reaction mixture is filtered through a glass filter funnel to remove the precipitated ammonium chloride. The hexane was decompressed (28 mmHg, 60
° C) and removed from the filtrate as a clear oil [(CH ₃
SiHNH) _0.8 (CH ₃ SiCH = CH ₂ NH) _0.2 ] _X
(150.7 g, 2.34 mol, 94% yield).
The oil has a viscosity of 43 cps (mPa) at 25 ° C and 5
It has a molecular weight of 60 g / mol.

The 100 ml one neck flask has a stir bar and septum and is sparged with nitrogen. The flask was then charged with the ammonolysis product and N-methylurea as shown in Table 1. The flask is placed in an oil bath on a stir / hot plate, and the septum is replaced with a water condenser capped with a septum. A nitrogen inlet needle and an oil bubble outlet are located within the septum. The reaction mixture is then heated to the temperature shown in Table 1 for 20 hours. Hydrogen gas evolution is observed. After completion of the reaction, the product is transferred to a suitable storage container under a nitrogen atmosphere. The viscosity is measured using a Brookfield cone and plate viscometer. "gel"
The term is used in the table below when a solid is formed

Table 1 Temperature (° C.) Wt. % (Mol%) Viscosity (mPa) 130 0.5 (0.4) 1085 130 1.0 (0.5) Gel 130 2.0 (1.8) Gel 130 3.1 (2.8) Gel 90 1.0 (0.9) 904 120 1.0 (0.9) 7817

Example 2 A vinyl-substituted silazane ammonolysis product is prepared as described in Example 1 and then reacted with acetamide according to the method described in Example 1. Acetamide sublimes from the reaction mixture above its melting point (79-81 ° C). 130 ° C.
Is reached, the flask is warm enough to allow the sublimed acetamide to melt and be returned to the pot.

Until this occurs, the reaction is not homogeneous. The reaction temperature, the amount of acetamide used and the viscosity of the product are shown in Table 2.

Table 2 Temperature (° C.) Wt. % (Mol%) Viscosity (mPa) 130 0.5 (0.6) 425 130 1.0 (1.1) 896 130 2.0 (2.2) 14,658 130 4.0 (4.5) 224,685 150 1.8 (2.0) Gel 140 2.8 (3.1) Gel

Example 3 The vinyl-substituted silazane ammonolysis product was prepared in Example 1
And then reacted with formamide according to the method described in Example 1. The reaction temperature, the amount of formamide used and the viscosity of the product are shown in Table 3.

Table 3 Temperature (° C.) Wt. % (Mol%) Viscosity (mPa) 130 0.6 (0.9) 2973 130 0.9 (1.3) Gel 130 1.2 (1.7) Gel 110 0.3 (0.4) 1085 110 0.6 (0.9) 3421 90 1.2 (1.7) gel

Example 4 Using the procedure described in Example 1, dimethylformamide was reacted with a vinyl-substituted silazane ammonolysis product prepared as described in Example 1. Table 4 shows the reaction temperature, the amount of dimethylformamide used, and the viscosity of the product.

Table 4 Temperature (° C.) Weight% (mol%) Viscosity (mPa) 130 2.0 (1.8) 1180 130 4.0 (3.7) 3610 130 5.0 (4.6) Gel 130 20.0 (22.0) solid

Example 5 Using the procedure described in Example 1, thiobenzamide was converted to
Reaction with a vinyl-substituted silazane ammonolysis product prepared as described in Example 1. Table 5 shows the reaction temperature, the amount of thiobenzamide used, and the viscosity of the product.

Table 5 Temperature (° C.) Weight% (mol%) Viscosity (mPa) 130 4.7 (2.3) 1,455 130 9.2 (4.7) 19,268

Example 6 Using the procedure described in Example 1, N-methylthiourea was reacted with a vinyl-substituted silazane ammonolysis product prepared as described in Example 1. Table 6 shows the reaction temperature, the amount of N-methylthiourea and the viscosity of the product.

Table 6 Temperature (° C.) Weight% (mol%) Viscosity (mPa) 90 1.0 (0.7) 407 120 1.0 (0.7) 2437 120 0.5 (0.4) 1271

Example 7 A 1 oz glass vessel was fitted with a stir bar and septum and purged with nitrogen. The vessel was charged with 2.0% by weight acetamide and acetamide-modified polysilazane prepared as described in Example 2 using a reaction temperature of 130 ° C. Dicumyl peroxide (0.5% by weight) was added.
A nitrogen atmosphere was maintained in the vessel using a nitrogen introduction needle and the reaction mixture was heated in an oil bath. Temperature 130
Upon reaching １４０140 ° C., the reaction mixture changed from a clear oil to an opaque solid. Thermogravimetric analysis (TGA) was performed (10 ° C / min, nitrogen atmosphere, 25-950 ° C). The solid amide-modified polysilazane had a TGA yield of 77% by weight of the black ceramic material.

Example 8 Acetamide-modified polysilazane was prepared as described in Example 2 using 1% by weight of acetamide and a reaction temperature of 130 ° C. The liquid polysilazane was thermoset to a solid and thermogravimetric analysis was performed as described in Example 6. The solid polysilazane had a TGA yield of 79% by weight of the black ceramic material.

Example 9 A formamide-modified polysilazane was prepared as described in Example 3, using 0.6% by weight of formamide and a reaction temperature of 120 ° C. The liquid polysilazane had a TGA yield of 61% by weight (20 ° C./min, nitrogen atmosphere, 25-950 ° C.).

Next, as described in Example 6, the formamide-modified polysilazane was thermally cured to a solid. The solid polysilazane is 73% T by weight of the black ceramic material.
It had a GA yield.

──────────────────────────────────────────────────の Continued on the front page (73) Patent holder 594142403 1300 Marrows Road, New work, Delaware 19714-6077, United States of America (72) Joan Marie Schwark Inventor Wilmington, Delaware, United States of America 19804 Bentwood Court 2056 (56) References JP-A-2-222455 (JP, A) JP-A-3-252425 (JP, A) JP-A-62-290730 (JP, A) JP-A-60-226890 ( JP, A) JP-A-1-129029 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08G 77/62 C01B 21/068

Claims (9)

(57) [Claims] 1. A (1) A mixture of ammonia or ammonia and a substituted or unsubstituted alkyl or aryl amines of 1-4 carbon atoms, RSiX _3, RR'SiX
_A silazane ammonolysis product is prepared by reacting with a silicon halide compound selected from ₂ and mixtures thereof, wherein X is Cl, Br or I, and R and R ′ are the same or different. , H, substituted or unsubstituted alkyl having 1 to 6 carbon atoms, aryl, alkenyl having 2 to 6 carbon atoms and alkynyl having 2 to 6 carbon atoms, and the reaction mixture has a Si-H bond. (2) a silazane ammonolysis product comprising at least one silicon halide compound having 0.1% to 30% by weight based on the weight of the ammonolysis product;
And (3) 3
A method for producing a silazane polymer by ammonolysis of an organohalosilane, wherein the method is heated to a temperature of 0 to 300 ° C. 2. The method according to claim 1, wherein the silicon halide compound further comprises RR ′
R "SiX, SiX ₄ or mixtures thereof (wherein R"
Has the same meaning as R and R '). 3. The method according to claim 1, further comprising heating to a temperature of 110 to 180 ° C. 4. The process according to claim 1, wherein the amount of the organic amide or thioamide used is from 0.5 to 5% by weight. 5. The polymer comprises at least one alkenyl or alkynyl group, and the polymer is cured by supplying energy to generate free radicals, or the polymer is exposed to UV light or electron beam radiation. The method according to any of the preceding claims, wherein the method is cured by: 6. A method according to claim 1, wherein at least one of the R group and the R ′ group is an alkenyl or alkynyl group having 2 to 6 carbon atoms, and supplies energy after the heating step to form free radicals to crosslink the polymer. The method of claim 5, further comprising: 7. The method according to claim 1, further comprising applying the polymer as an adhesive or sealant, as a film or coating, or as a binder.
7. The method according to any one of claims 1 to 6. 8. A method for producing a silicon nitride-containing ceramic from a polymer obtained by the method according to claim 1, wherein the polymer is at least 80% in an inert atmosphere or an ammonia-containing atmosphere.
A method comprising pyrolyzing at a temperature of 0 ° C. to obtain a silicon nitride-containing ceramic. 9. The method according to claim 8, wherein the obtained silicon nitride-containing ceramic is in the form of ceramic fibers or foam, or a composite structure.