1. Field of the Invention
The present invention relates to bis(silyl)alkanes represented by the formulas (III), (IV) and (V), respectively, and a method for their preparation. In accordance with the present invention, in order to prepare the bis(silyl)alkanes represented by the formulas (III), (IV) and (V) at the same time, an organic chloride, represented by the formula (I) and having a chloro at each side of its molecule, is first mixed with a hydrogen chloride or an alkyl chloride represented by the formula (II), said alkyl chloride being capable of generating the hydrogen chloride during its reaction, in order to provide a mixture. This result mixture is in turn directly reacted with a metal silicon. ##STR2## wherein R is H or a phenyl, R' is a hydrogen atom or a C.sub.1-4 alkyl and n is an integer ranging from 1 to 4.
If described in detail, the present invention provides a novel and improved method for preparation of three types of bis(silyl)alkanes, the first being represented by the formula (III) and having two dichlorosilyls, the second being represented by the formula (V) and having two trichlorosilyls and the third being represented by the formula (IV) and having one dichlorosilyl and one trichlorosilyl, at the same time. In order to prepare these bis(silyl)alkanes, a gaseous mixture prepared by mixing the organic chloride of the formula (I), having a chloro at each side of its molecule, with the hydrogen chloride or the alkyl chloride of the formula (II), said alkyl chloride being capable of generating the hydrogen chloride during its reaction process, is directly reacted with the metal silicon in a fluidized-bed reactor or an agitation reactor at a reaction temperature of 260.degree. C.-370.degree. C. in the presence of copper catalyst. Such bis(silyl)alkanes having the chlorohydrosilyls have a property of easily further reacting with an organic compound having an unsaturated bond. In this regard, they can be used as effective starting materials for preparation of silicon compounds having several types of organic functional groups.
2. Description of the Prior Art
U.S. Pat. No. 2,380,995 discloses a known method for preparation of methylchlorosilanes, including dimethylchlorosilane, by direct reaction of a metal silicon with an organic halogen compound in the presence of a copper catalyst as represented by the reaction formula (VI) and this known method has been generally used as a basic technique recently in the silicon industry. ##STR3##
From the above direct reaction of the formula (VI), the desired reaction product, dimethylchlorosilane, together with other reaction products, such as methyltrichlorosilane, trimethylchlorosilane, tetrachlorosilane and etc., are prepared. This direct reaction is a complex reaction which also provides additional side products, such as small amount of material having a high boiling point, and in which change of the reaction conditions causes variation of the composition of the reaction products, including the desired reaction product. In this regard, it is necessary to accurately select the reaction condition, such as degree of purity of starting materials, kind and amount of catalyst, kind and amount of cocatalyst, reaction temperature, reaction pressure and type of reactor used, in order to efficiently prepare the desired reaction product, that is, the dimethylchlorosilane, using the above direct reaction represented by the formula (VI). In this direct reaction of a metal silicon with an organic chloride, it has been noted that the reaction can not be efficiently carried out if a catalyst, most preferably copper, is not used. In addition, a metal, such as zinc, aluminum or cadmium, may be used as a cocatalyst of this reaction, as required. This cocatalyst is used in order to not only reduce the reaction start time but also to improve selectivity of the dimethylchlorosilane of the reaction products, that is, the methylchlorosilanes [E. G. Rochow, J. Am. Chem. Soc., 67, 963 (1945)]. When the amount of the copper catalyst used in this direct reaction is increased, there is a problem in that the chlorine content of the reaction products is increased even though the reaction is accomplished in a short time. In this regard, it has been noted that it is good to use the copper catalyst of 10% by weight of the silicon in this direct reaction wherein the silicon is reacted with methyl chloride.
It has been reported that the copper, the catalyst of the reaction of the formula (VI), causes a silicon bond of the metal silicon to .eta.-phase Cu.sub.3 Si and this Cu.sub.3 Si of the silicon bond is in turn reacted with the organic chloride [V. S. Fikhtengolts & A. L. Klebanskii, J. Gen. Chem. U.S.S.R., 27, 2535 (1957)]. In order to prepare the .eta.-phase Cu.sub.3 Si, there has been proposed two types of preparation processes, that is, a physical process wherein both copper and silicon are heated to temperatures of 800.degree. C.-1100.degree. C. in the presence of inert gas [P. Trambouze, & B. Imelik, J. Chim. Phys., 51, 505 (1954)] and a chemical process wherein cuprous chloride is reacted with silicon as represented by the reaction formula (VII) [R. J. H. Voorhoeve. & J. C. Vlugter, J. Catalysis, 4, 129 (1965)]. EQU nSi+CuCl.fwdarw.SiCl.sub.4 +Cu.sub.3 Si+Cu+(n-2)Si (VII)
Conventionally, the reaction of the silicon with the methyl chloride is a high temperature reaction which is carried out at a high temperature not lower than 300.degree. C. In addition, this reaction is an exothermic reaction. In this regard, the heat of this reaction not only causes the reactants to flocculate with each other but also introduces partial overheating if the excess heat if it is not efficiently removed [A. L. Klebamskii & V. S. Fikhtengolts, J. Gen. Chem. U.S.S.R., 27, 2693 (1957)]. Additionally, if the reaction temperature is higher than a predetermined proper temperature, this reaction results in reduction of the production amount of the desired dimethylchlorosilane as well as introduction of several side reactions. Such a high reaction temperature also causes the methyl chloride, the start material, and the reaction products to be decomposed and, as a result, carbons to be deposited on the silicon surfaces. As a result, silicon activity is rapidly deteriorated [J. C. Vlugter & R. J. H. Voorhoeve, Conf. Accad. Lincei, Alta Tech. Chim. 1961, p 81 (1962)]. In this regard, it is very important to control the reaction temperature in preparation of methylchlorosilanes in accordance with the direct reaction of the formula (VI).
In the direct reaction of the formula (VI), three types of reactors, otherwise stated, stationary type, agitation type and fluidized-bed type reactors are generally used. The agitation reactors have an advantage in that its temperature control is more easily carried out in comparison with the stationary reactor. It provides good reactivity since it causes the solid particles to collide with each other and, as a result, refresh their surfaces. Conventionally, since the copper catalyst of this reaction, has a density of three times of the silicon reactant of this reaction, it is very difficult to effectively mix the two materials with each other.
In order to overcome this problem, there has been proposed a method wherein the reaction is carried out under the condition that the solids at the bottom of the reactor are forced to move upwards by a spiral agitator and, at the same time, gaseous organic chloride is blown upwards [J. E. Sellers & J. L. Davis, U.S. Pat. No. 2,449,821]. However, this method requires reacting strong corrosive organic chloride with other reactants at a high temperature. In this respect, this method has a problem in that is necessarily requires a reactor having such excellent corrosion resistance that the reactor sufficiently resists the corrosive organic chloride. However, such a reactor can not be easily obtained. Furthermore, it is noted that this method is not proper for mass production of the desired reaction product and continuous reaction process.
In order to solve the above problems introduced by the known method such as disclosed in the above U.S. Pat. No. 2,449,821, several type of fluidized-bed reactors have been proposed such as disclosed in U.S. Pat. No. 2,887,502 of B. A. Bluestrin. In this fluidized-bed reactor, silicon and copper are reacted with each other under the condition that methyl chloride is blown upwards and, at the same time, the silicon and the copper are fluidized. This method using the fluidized-bed reactor efficiently removes the heat of reaction and, in this respect, is widely used in preparation of methylchlorosilanes.
Meanwhile, it is possible to prepare organic silicon compounds by directly reacting organic material, having at least two halogen atoms bonded thereto, with metal silicon. For example, U.S. Pat. Nos. 2,381,000, 2,381,001 and 2,381,002 disclose that a linear or cyclic chlorosilaalkane is prepared, as represented by the reaction formula (VIII), by reaction of methylene chloride with silicon in a fluidized-bed reactor. However, the prior art including the above U.S. Patents have not reported on accurate yield of the reaction products. ##STR4##
In reaction with the metal silicon, the methylene chloride can be reacted with the metal silicon at a relatively lower temperature in comparison with the methyl chloride. However, this reaction, wherein the methylene chloride is reacted with the metal chloride, results in dechlorination as well as dehydrochlorination at a high reaction temperature of about 300.degree. C. since the methylene chloride has an excellent reactivity. In this respect, this reaction produces several types of reaction products. Thus in this reaction, the reactants are decomposed into chlorines and hydrogen chlorides simultaneously with generation of carbons. These carbons are deposited on the surfaces of silicons and this causes the activity of the silicons to be rapidly deteriorated.
G. Fritz et al. reported on that when the above reaction was carried out using a fluidized-bed type reactor at a reaction temperature of 320.degree. C., the production amount of the reaction products having high molecular weight is increased [G. Fritz & A. Worsching, Z. Anorg. Allg. Chem., 512, 131 (1984)].
The aforementioned reaction generally produces five kinds of reaction products. Otherwise stated, this reaction produces bis(silyl)alkanes, which are compounds having two dichlorosilyls, two trichlorosilyls or one dichlorosilyl and one trichlorosilyl, a straight chain carbosilane such as 1,3,5-trisilapentane or 1,3,5,7-tetrasilaheptane, a cyclic carbosilane which is a compound having a long substituent at its silicon and a cyclic carbosilane which is a compound having a long substituent at its carbon. This reaction also produces a high-molecular compound similar to molasses or tar. However, it has been noted that no reaction product of the above products has yield higher than 30%, and furthermore, the maximum yield of a reaction product is about 20% at the most [G. Fritz & E. Tatern, "Carbosilanes-Syntheses and reactions", Spring-Verlag, New York, 1986]. G. Fritz et al. reported that in accordance with a reaction of methylene chloride with metal silicon, bis(trichlorosilyl)(dichlorosilyl)alkane having Si--H bond was prepared in the form of side product of 3% [G. Fritz & H. Thielking, Z. Anorg. Allgem. Chem., 306, 39 (1960)].
The present inventors proposed that as represented by the reaction formula (VIIII), trisilaalkane as a reaction product and disilaalkane as a side product were prepared, using an agitation reactor having a spiral agitator or a fluidized-bed reactor, by a direct reaction of silanes having chloromethyl with silicon under the condition that the reaction temperature was controlled not to be higher than 350.degree. C. and, at the same time, the copper catalyst is controlled in its using amount to be 10-15%. In addition, it was noted that the fluidity of the reactants together with the reactivity and selectivity of silicon is improved when spherical fine powder of acid white clay of 5-50% by weight of the silicon was added to the reaction in order to promote the fluidization of the reactants [Korean Patent Appln. No. 91-1055]. ##STR5## wherein R.sup.1, R.sup.2 and R.sup.3 are a methyl or a chloro, respectively.
In addition, the present inventors proposed that as represented by the reaction formula (X), two kinds of bis(silyl)methanes were prepared when the compound represented by the formula (II) is used as a source of hydrogen chloride in a reaction of silanes having chloromethyl with metal silicon. The compound of the formula (II) is selected from, for example, 1,2-diethane chloride or hydrogen chloride, propyl chloride, n-butyl chloride and t-butyl chloride. In addition, it is preferred to use organic chlorides, such as hydrogen chlorides or butyl chlorides which are easily decomposed at the reaction temperature in order to generate hydrogen chloride [Korean Patent Appln. No. 91-24243]. ##STR6## wherein R.sup.1, R.sup.2 and R.sup.3 are a methyl or a chlorine, respectively, R is C.sub.1-4 alkyl, H, Cl or CH.sub.2 CH.sub.2 Cl.