KR20160040438A - Method for producing thermoplastic pre-ceramic polymers - Google Patents

Abstract

The present invention also relates to a process for the preparation of high molecular weight, solid, meltable, thermoplastic, pre-ceramic polymeric articles by the conversion of liquid low molecular weight polysilazanes in a solvent in the presence of a catalyst, And a method for producing the same. The polysilazanes obtained can be used in a wide variety of industrial applications such as extrusion, injection molding, melt spinning, knife rendering, film and hollow body blowing, rotational molding, fluidized bed sintering, flame spraying and transfer molding (RTM and DP- RTM).

Description

[0001] METHOD FOR PRODUCING THERMOPLASTIC PRE-CERAMIC POLYMERS [0002]

The field of ceramic materials can in principle be subdivided into silicates used for versatile and sanitary ceramics and high performance ceramics used for engineering ceramics (Ralf Riedel, Aleksander Gurlo, Emanuel lonescu, "Chem. Unserer Zeit ", 2010, 44, 208-227). High performance ceramics include ceramics formed based on oxide materials (e.g., Al ₂ O ₃ ) and nonoxide materials.

These include, for example, ceramics based on silicon nitride (Si ₃ N ₄ ) and silicon nitride carbide (SiCN) with exceptional thermomechanical properties. For example, according to the stoichiometry of their compositions, it is known that silicon nitride carbide in an inert atmosphere has a tendency not to crystallize up to about 1350 DEG C (see Christoph Konetschny, Dusan Galusek, Stefan Reschke, Claudia Fasel, Ralf Riedel, "Journal of the European Ceramic Society ", 19, 1999, pages 2789-2769). In air, their stability extends to 1500 ° C.

High performance ceramics such as Si ₃ N ₄ and SiCN ceramics have been used in high temperature applications (energy technology, automotive construction, aerospace, etc.) due to their properties, biomedical engineering, Or, alternatively, as a functional material in microelectronics.

The manufacture of ceramic components generally involves some form of powder engineering processing. This means that the starting material in powder form is injected in a form that is subsequently densified (i.e., sintered) without the occurrence of melting.

This procedure is the only procedure that can be used for pure metal oxide- and nitride-based ceramics because the melting point of these ceramic materials is too high for some processing or because the material is pre-decomposed . Processing by injection molding or conventional casting methods involving the use of classical and industrially customary shaping techniques, e.g., liquid or molten materials, would be desirable, Time is greatly reduced, material consumption is reduced, and the energy demand is also reduced.

In contrast, pre-ceramic, silicon-based polymers are known for making non-oxide ceramic materials in silicon-carbon-nitrogen (SiCN) systems. In order to use these pre-ceramic polymers in industrial, continuous processes, their properties must be reproducible and have long-term stability.

The commercial availability of suitable starting materials should be presupposed. At the same time, for this reason, resource conservation and therefore inexpensive conversion are important for a wide range of industrial uses.

The only pre-ceramic polymer for making SiCN ceramics that satisfies the requirements of commercial availability on a ton scale at an acceptable price is the organopolysilazane (OPSZ), hereinafter referred to as polysilazane, herein. Polysilazanes (e.g., KiON ML 33 and KiON HTT 1800) are currently available from AZ Electronic Materials and Clariant. The preparation is via the liquid ammonia process as described in EP 1232162 B1.

The polysilazane obtained as described in EP 1232162 B1 is liquid and has a low viscosity (<50 mPa * s) and a relatively low molecular weight (<2500 g / mol). Liquid polysilazanes have the critical theoretical disadvantage that they can not be used for some of the processing techniques already mentioned above. The classical processing techniques (e.g., extrusion) of the polymer industry can not be used as well. A further disadvantage of liquid polysilazanes of the type described by EP 1232162 B1 is their relatively low molecular weight. These disadvantages are the ultimate cause for low ceramic yield. Therefore, it is preferable to produce a high molecular weight, solid-soluble polysilazane from such a liquid polysilazane.

Therefore, there is a desperate need for a procedure for converting the above-described low viscosity liquid polysilazane to a high molecular weight solid soluble polysilazane. This procedure must provide a reproducible polymer that not only has a high molecular weight, but is thermally stable, meltable and soluble. They are storage stable for at least 12 months and can be processed using industrial procedures. Examples include extrusion, injection molding, melt spinning, calendering, film blowing, blow molding, rotational molding, fluidized bed sintering, flame spraying and transfer molding (RTM and / or DP- ).

The literature describes a very wide variety of procedures for converting liquid silane-based pre-ceramic polymers into solid precursors.

The use of solid basic catalysts plays a large role here. EP 332357 A1 describes the use of alkoxides to increase the molecular weight of liquid starting materials and to obtain solid products.

• It is true that the product thus obtained has a higher ceramic yield than the starting material, but the reproducibility of the procedure is limited and the product is highly crosslinked and therefore generally insoluble and insoluble; Thus, if possible, all further processing is possible only in the presence of great difficulty.

• The use of Lewis-acidic materials is similarly known. However, this is not suitable for commercially available raw materials because it results in an insoluble product.

Additional procedures for increasing the molecular weight include, but are not limited to, the action of transition metal complexes, By Y. Blum or by She (Z. Xie), X. X. Hu, Z. Fan, W. W. Peng, X. X. Li, W. W. Gao, X. X. Deng, Queue. The use of ruthenium carbonyls as described by Q. Wang. In addition, a highly crosslinked polymer is obtained, the ceramic yield is high, but the product is insoluble and insoluble, so further processing is not possible. Applications to commercially available polysilazanes were unsuccessful and no changes in molecular weight or physical state were observed.

Gaseous materials have been used to increase the molecular weight of polysilazanes. Examples are gas mixtures (EP 412915 A1) consisting of BH ₃ (US 5262553 A), NH ₃ -H ₂ O, HCl and HBr mixtures or else ozone.

A combination of hydrogenation, hydrogenation, ammoxidation and subsequent thermal post-treatment has been described for the preparation of ABSE (ammonia decomposed bis-silylethane) precursor polycarbosilazane (cf. S. Kokott, G , &Quot; Soft Materials "(2007), Volume Date 2006, 4 (2-4), 165-174). The ABSE precursor is not commercially available, and thermal post-treatment does not establish reproducible properties.

The use of ammonium salts has been described very early by Muller and Rochow (cf. Carl R. Kruger, Eugene G. Rochow, "Journal of Polymer Science &quot;, Part A, Vol. 1964), page 3179). The liquid polysilazane was heated vigorously in the presence of NH ₄ Cl, NH ₄ Br or NH ₄ I to obtain the waxy phase product. Corey Wu (Corriu) (See also the literature [RJP Corriu, D. Leckercq, PH Mutin, JM Planeix, A. Vioux, "Journal of Organometallic Chemistry", 406, 1991, S. C1]) is being used Bu ₄ NF , And increased molecular weight. In these cases, a finally insoluble and insoluble product (thermosetting) was obtained. No further processing was achieved.

In summary, the methods described above are unsuitable for industrial processes that do not meet or are unable to meet the requirements for reproducible procedures in which solid high molecular weight polymers are soluble and meltable, or which use commercially available raw materials.

It has surprisingly been found that the combination of a specific reaction medium, a limited amount of catalyst, the use of a precise stopper, the concentration of the starting material established in a limited manner, and the reaction temperature surprisingly leads to the invention providing a commercially available liquid polysilazane, To ensure reproducible conversion to solid, molten and soluble products. The method is remarkable in that the polymer properties (molecular weight, softening range) of the solid product can be established precisely by changing the reaction conditions.

The present invention therefore also relates to a process for the preparation of high molecular weight, meltable thermoplastic pre-ceramic polymers which comprises reacting liquid low molecular weight polysilazanes in a solvent in the presence of a catalyst and terminating the reaction with an immediate stopping agent, Ceramic thermoplastic pre-ceramics polymer, comprising the steps of:

The liquid low molecular weight polysilazane used is preferably a polysilazane of the formula (1) or a mixture of polysilazanes of the formula (1).

In Formula 1,

R ', R "and R'" are the same or different and each independently represent hydrogen or an optionally substituted alkyl, aryl, vinyl, or (trialkoxysilyl) alkyl radical,

n represents an integer such that the polysilazane has a number average molecular weight of 150 to 150,000 g / mol.

Polysilazanes having particular suitability in the present invention are those wherein R ', R "and R'" are each independently selected from the group consisting of hydrogen, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, , Tolyl, vinyl, 3- (triethoxysilyl) propyl, and 3- (trimethoxysilylpropyl).

One preferred embodiment utilizes a perhydropolysilazane of formula (2).

In Formula 2,

n represents an integer such that polysilazane has a number average molecular weight of 150 to 150,000 g / mol.

The starting reagent used in a further preferred embodiment is the polysilazane of formula (III).

In Formula 3,

R ', R ", R", R ^* , R ^** and R ^*** each independently represent hydrogen or an optionally substituted alkyl, aryl, vinyl or (trialkoxysilyl) alkyl radical,

n and p are such that the polysilazane has a number average molecular weight of 150 to 150,000 g / mol.

The following compounds are particularly preferred:

- a compound in which R ', R "' and R ^*** represent hydrogen and R", R ^* and R ^** represent methyl;

- a compound in which R ', R''' and R ^*** denote hydrogen, R '', R ^* denotes methyl and R ^** denotes vinyl;

- R ', R''', R ^* and R ^*** denote hydrogen and R '' and R ^** denote methyl.

This can be explained by taking as an example the raw materials of KiON ML 33 and HTT 1800 used:

It is likewise preferable to use the polysilazane represented by the formula (4).

In Formula 4,

R ', R'', R ''', R *, R **, R ***, R 1, R 2 and R ³ are each independently hydrogen or an optionally substituted alkyl, aryl, vinyl or (tri Alkoxysilyl) alkyl radical,

n, p and q are such that the polysilazane has a number average molecular weight of 150 to 150,000 g / mol.

R 1, R '"and R ^*** represent hydrogen, R", R ^* , R ^** and R ² represent methyl, R ³ represents (triethoxysilyl) propyl, and R ¹ A compound showing this alkyl or hydrogen is particularly preferred.

The concentration of the polysilazane source used in the reaction medium is chosen to ensure sufficient mixing. The concentration range selected in the present invention extends from 20 wt% to 80 wt%. A range of 30 to 70% by weight is particularly preferred, and a range of 33 to 66% by weight is very particularly preferred.

The reaction medium suitably comprises, in particular, an organic solvent which does not comprise any water or reactive groups (e.g. hydroxyl or amine groups). Examples include aliphatic or aromatic hydrocarbons, (hydro) halocarbons, esters such as ethyl acetate or butyl acetate, ketones such as acetone or methyl ethyl ketone, ethers such as tetrahydrofuran or dibutyl Ethers, and also mono- and polyalkylene glycol dialkyl ethers (glymes) or mixtures thereof.

The reaction medium used in particular includes aprotic solvents such as diethyl ether, cyclohexane, HMPTA, THF, toluene, chlorinated hydrocarbons, pentane, hexane and dibutyl ether. THF, toluene, chlorinated hydrocarbons, diethyl ether and dibutyl ether are particularly preferred.

The process may be carried out in a temperature range of -20 to 110 캜, with a range of 0 to 80 캜 being preferred, and a temperature range of 15 to 50 캜 very particularly preferred.

The process can be carried out in a pressure range from 300 mbar to 30 bar, with a range from 500 mbar to 5 bar being preferred and a pressure range from 750 mbar to 3 bar being very particularly preferred.

The catalysts used include chlorides, bromides, iodides, fluorides and hydroxides of tetraalkyl substituted ammonium salts. Examples include, but are not limited to, tetramethylammonium chloride, tetramethylammonium bromide, tetramethylammonium iodide, tetramethylammonium fluoride, tetraethylammonium chloride, tetraethylammonium bromide, tetraethylammonium iodide, tetraethylammonium fluoride, tetraethylammonium fluoride, Butyl ammonium chloride, tetrabutyl ammonium bromide, tetrabutyl ammonium iodide, tetrabutyl ammonium fluoride, as well as Schwesinger catalysts and phase transfer catalysts (PiP). Particular preference is given to tetrabutylammonium salts and Schwäbinger reagents.

The concentration of the catalyst should preferably be selected in the range of 0.01 to 10% by weight. Concentrations of 0.1 to 5% by weight are particularly preferred. A very particularly preferred range is from 0.15 to 2% by weight.

The reaction produces gaseous products (hydrogen, ammonia, silane). Thus, accurate timing for catalyst mixing is advantageous. Thus, mixing within 10 to 200 minutes is preferred, and very particularly preferred in the range of 20 to 100 minutes.

Since the silazanes used are sensitive to oxidation and hydrolysis, the process is advantageously carried out under protective gas.

Useful blocking agent includes, for example, the hydrides of alkali metals and alkaline earth metals, in particular, KH, NaH, LiH, CaH 2, LiAlH 4, Ca (BH 4) 2 and NaBH _4. NaH, LiAlH _4, NaBH _4, and the Ca (BH _{4) 2} in particular priority.

The stopping agent should be added in a timely dissolved form. Useful quencher solvents include, among others, substances mentioned for use as reaction media. The concentration of the stopper in the solution should be 2 to 70%, preferably 3 to 30%, and most preferably 5 to 10%. The stopping agent mixing time can be determined by the released hydrogen gas tracing. The preferred time for stopper mixing is reached when the flow rate of hydrogen is reduced to 1/10 of its maximum value.

The product can be isolated, for example, by crystallization at low temperature and subsequent filtration, or by concentration of the reaction mixture.

The final product is characterized by the molecular weight distribution measurement of the final product by GPC and the softening range of the final product. A rheological study provides information on the degree of crosslinking.

The product formed is a solid polysilazane having a molecular weight of at least 2,000 to 2 million g / mol, especially 10,000 to 1 million g / mol. The degree of crosslinking and thus the softening range can be established anywhere between -15 and 180 [deg.] C through the choice of reaction conditions. The resulting product, if properly stored, has a shelf life of at least 12 months and can be dissolved at any time in commonly used polar and nonpolar aprotic solvents. Insufficient monitoring of the reaction conditions causes insoluble, insoluble materials to be obtained.

Preferred solvents for dissolution include, for example, ether (THF) and nonpolar hydrocarbons (hexane, petroleum ether).

These polysilazanes obtained using the process of the present invention can be obtained in a reproducible manner, are thermally stable, meltable, soluble and have a high molecular weight. They are stable in storage for more than 12 months and can be used in a wide range of applications including conventional industrial processes such as extrusion, injection molding, melt spinning, calendaring, film blowing, blow molding, rotary molding, fluidized bed sintering, / RTI &gt; and / or DP-RTM). &Lt; / RTI &gt;

Example 1 of the present invention

3.0 kg of KiON ML 33 and 1.5 kg of THF were mixed with a solution of 27.1 g of tetrabutylammonium fluoride (TBAF) dissolved in 513 g of THF at room temperature over 40 minutes. Mixed , The mixture was further stirred for 30 minutes and then mixed with 7.5 g of Ca (BH ₄ ) ₂ suspended in 133.5 g of THF. The mixture was stirred for an additional 35 minutes. The THF was finally removed under elevated temperature and the pressure was reduced leaving 2.76 kg of solid polysilazane having a softening point of ~ 90 ° C and an M _w of 38,000 g / mol.

Example 2 of the present invention

100 g of KiON ML 33 and 0.2 kg of THF were mixed with a solution of 0.26 g of TBAF dissolved in 20 g of THF at room temperature over 40 minutes. Upon completion of the mixing, the mixture was further stirred for 90 minutes and then mixed with 0.25 g of Ca (BH ₄ ) ₂ suspended in 5 ml of THF. The mixture was stirred for an additional 30 minutes. The THF was finally removed under elevated temperature and the pressure was reduced leaving 87.9 g of solid polysilazane having a softening point of ~ 50 ° C and an M _w of 4,190 g / mol.

Example 3 of the present invention

An argon-inactivated 2 l four-necked flask equipped with a stirrer, thermometer and condenser was first charged with 0.075 kg of THF and 150 g of devolatilized KiON HTT 1800. A solution of 0.375 mg of TBAF dissolved in 27.16 ml of THF was added over 30 minutes. After 30 minutes of subsequent stirring, the reaction solution was mixed with 375 mg of Ca (BH ₄ ) _{2 in} 7.5 ml of THF to terminate the reaction. The solvent was removed to leave a white solid having a M _w of 116,000 g / mol solidified at about 110 ° C.

Example 4 of the present invention

A nitrogen-deactivated 1 L one-necked flask equipped with magnetic core and condenser was first charged at room temperature with 200 g THF, 100 g KiON HTT 1800 and 100 g KiON ML 33. The homogeneous mixture was mixed with a solution containing 500 mg of TBAF in 38.2 ml of THF over 60 minutes. After subsequent stirring for 30 minutes, thereby terminating the reaction with 10 ml THF in the Ca (BH _{4) 2} 491mg. The left has a softening point and 10,100g / mol for M _w molecular weight of about 60 ℃ solids by distillation.

Example 5 of the present invention

An argon-deactivated 1.1 liter flask equipped with magnetic core and condenser was first charged at room temperature with 200 g of diethyl ether and 100 g of Ceraset PSZ 20 and the initial charge was mixed thoroughly. A mixture of 1 ml of 1 M TBAF / THF solution and 19 ml of diethyl ether was mixed over 5 minutes. An additional 30 min reaction, Ca (BH ₄ ) _{2 in} diethyl ether After mixing 0.25 g and stirring for an additional 30 minutes, the solvent was removed to leave a melt which was viscous at 115 [deg.] C and was glassy to solidify upon cooling. M _w = 21,300 g / mol.

Embodiment 6 of the present invention

The inactivated 500 ml flask was charged with 80 g of toluene and 40 g of Ceraset PSZ 20. A solution of 0.4 ml of 1 M tetrabutylammonium hydroxide and 7.6 ml of toluene was mixed over 10 minutes and then stirred for 25 minutes. A mixture of ₂ ml of toluene and 0.1 g of suspended Ca (BH ₄ ) ₂ completely stopped the reaction. The solvent was removed to leave a waxy solid at room temperature with a M _w of 20,900 g / mol.

Example 7 of the present invention

300 g of THF was mixed with 600 g of KiON ML 33 in a 4 l flask. 6 ml of a 1 M TBAF solution diluted with 114 ml of THF was added over 30 minutes, followed by further stirring for 30 minutes. The reaction was quenched with LiBH4 &lt; _{RTI ID = 0.0} &gt; 14 mmol). After filtration and solvent removal, a glassy solidified melt was obtained. M _w is 17,350 g / mol.

Example 8 of the present invention

0.22 ml of a 0.3 M solution of tetrakis [tris (dimethylamino) phosphoranylideneamino] phosphonium fluoride in benzene was first charged to 40 ml of THF and mixed with 10 g of KiON HTT 1800 over 10 minutes. The reaction was quenched with Ca (BH ₄ ) ₂ and the solvent was removed to give a solid with an M _w of 6,200 g / mol.

Example 9 of the present invention

300 g of THF was mixed with 600 g of KiON ML 33 in a 4 l flask. 6 ml of a 1 M TBAF solution diluted with 114 ml of THF was added over 30 minutes, followed by stirring for 30 minutes. The reaction was quenched using 14 mmol of NaH in 7 ml of THF. After filtration and solvent removal, a glassy solidified melt was obtained. M _w is 28,840 g / mol.

Embodiment 10 of the present invention

90 g of KiON HTT 1800 and 210 g of THF were charged first and cooled to 0 占 폚. Under vigorous stirring, 15 ml of dissolved THF and 450 mg of TBAF dissolved therein were added over 60 minutes. After subsequently stirring the mixture at 0 ℃ 60 minutes, and warmed to 20 ℃, in THF 50ml Ca (BH ₄₎ the reaction was stopped using a ₂ 300mg. The THF was removed by distillation to leave a waxy solid having an M _w of 1,650 g / mol.

Comparative Example 1

300 g of THF was mixed with 600 g of KiON ML 33 in a 4 l flask. 6 ml of a 1 M TBAF solution diluted in 114 ml of THF was added over 30 minutes and allowed to stir overnight. Filtration and distillation of the solvent left insoluble and insoluble solids.

Comparative Example 2

A nitrogen-deactivated 1 L one-necked flask equipped with magnetic core and condenser was first charged with 100 g THF, 100 g KiON HTT 1800, and 100 g KiON ML 33 at room temperature. The homogeneous mixture was mixed over 45 minutes with a solution containing 1500 mg of TBAF in 38.2 ml of THF. After subsequent 30 minutes of stirring, formation of a white solid with a rapid increase in mass can be achieved. The solids are insoluble and insoluble.

Comparative Example 3

200 ml of KiON ML 33 was initially charged in a 500 ml three-necked flask and mixed with 5 ml of 1 M TBAF / THF solution under vigorous stirring. A white solid was formed at the drop entry point. After completion of the mixing, the contents were stirred for 60 minutes to obtain two-phase flask contents. The removed solid is insoluble and does not melt.

Claims (11)

A process for preparing high molecular weight, solid, meltable, thermoplastic pre-ceramic polymers comprising reacting liquid low molecular weight polysilazanes in a solvent in the presence of a catalyst and terminating the reaction with an immediate stopping agent to the desired degree of polymerization Wherein the high molecular weight, meltable, thermoplastic, 3. The method of claim 1, wherein a mixture of polysilazanes of formula (1) or polysilazanes of formula (1) is used.
[Chemical Formula 1]

In Formula 1,
R ', R "and R'" are the same or different and each independently represent hydrogen or an optionally substituted alkyl, aryl, vinyl or (trialkoxysilyl) alkyl radical,
n represents an integer such that the polysilazane has a number average molecular weight of 150 to 150,000 g / mol. 3. A compound according to claim 2, wherein R ', R "and R'" each independently represent hydrogen, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert- - (triethoxysilyl) propyl, and 3- (trimethoxysilylpropyl). &Lt; / RTI &gt; 4. Process according to one or more of claims 1 to 3, wherein the perhydro polysilazane of formula (2) is used.
(2)

In Formula 2,
n represents an integer such that polysilazane has a number average molecular weight of 150 to 150,000 g / mol. 5. Process according to any one of claims 1 to 4, wherein chlorides, bromides, iodides, fluorides and hydroxides of tetraalkyl substituted ammonium salts are used as catalysts. 6. The process according to any one of claims 1 to 5, wherein the concentration of the catalyst in the reaction mixture ranges from 0.01 to 10% by weight. 7. A process according to any one of claims 1 to 6, wherein a hydride of an alkali metal and a hydride of an alkaline earth metal are used as a stopping agent. 8. A process according to any one of claims 1 to 7, wherein the solvent used comprises water and also an organic solvent which does not contain a reactive group, especially an aliphatic or aromatic hydrocarbon. 9. Process according to at least one of claims 1 to 8, wherein the concentration of the starting materials in the reaction medium is in the range of 20 to 80% by weight. A high molecular weight, solid, meltable thermoplastic pre-ceramic polymer obtainable by a process according to one or more of claims 1 to 9. The method of claim 10, further comprising the steps of applying a coating composition to a substrate, such as a substrate, using conventional industrial procedures such as extrusion, injection molding, melt spinning, knife rendering, film blowing, blow molding, spin molding, fluidized bed sintering, flame spraying, A high molecular weight, solid, meltable, thermoplastic pre-ceramic polymer that can be processed using molding (RTM and / or DP-RTM).