Dunnavant, W. R.

Marrkle, R. A.

English

NASA Technical Reports Server

NATIONAL AERONAUTICS AND SPACE AB 
WASHINGTON, D.C. 20546 
(CODE) 
5, 
L
&Lo 
t (CATEGORY) 
REPLY TO 
A m  OF: 
0: c sc Technical I n f o m a t i o n  D 
t t n :  M i s s  Winnie M e  Morgan 
GP/Office of A s s i s t a n t  General 
Counsel for Pa ten t  Matters 
nnouncement of NASA-Owned U . S .  Pa ten t s  i n  S 
nce with t h e  p ocedures contained i n  the Code GP 
t o  Code US% memorandum on t h i s  s u b j e c t ,  dated June 8, 1970, 
a b s t r a c t i n g  and announcement i n  MAS 
SA-owned U , S  pa ten t  a fo 
U , S ,  Patent  
Corporate Source 
Supplementary 
corpora te  Source 
NASA Pa ten t  C a s e  N o ,  
nt covers am. invent ion  
§305(a) of t h e  
SA appears on the  
i f i c a t i o n  8 
an invent ion  of, B I ?  9 5 )  
Gayle Parker 
Enclosure : 
copy of Pa ten t  
i t h  respect 
https://ntrs.nasa.gov/search.jsp?R=19710013754 2020-03-17T03:02:04+00:00Z
ate 
I t  is therefore an object of this invention to provide a 
process for preparing dianilinosilanes in high-purity form. 
Another 'object is to provide a process for preparing 
dianilinosilanes wherein a high yield is obtained. 
Other objects and advantages of the invention will be 
apparent from the following description. 
In  the present invention dianilinosilanes are prepared 
by reacting a dichlorosilane with aniline in the presence 
u. 60-448.2 8 claims of 2,4,6-trimethylpyridine (s-collidine). A high degree of 
10 purity is obtained reproducibly by this means, and prod- 
uct yield is substantially increased. This process is readily 
amenable to scale up for production of large quantities 
of dianilinosilane suitable for use in polymer synthesis, 
Dianilinosilanes are prepared by reacting a dichbro- Although this invention is not to be understood as lim- 
silane with aniline in the presence of 2,4,6-wimethylpyri- 15 ited to a Particular theory, it is postulated that the im- 
dine (s-collidine) in a n  organic solvent. By-product ani- proved Purity and yield largely result from fdimination d 
line hydrochloride is removed from the reaction mixture undesirable side-reactions. The previously known reaction 
by precipitation as a hydrochloride salt of the s-collidine. Of diphenyldichlorosilane with aniline proceeds as fol- 
Contaminating side-reactions are avoided, and a high- lows: 
3,433,818 
@CESS FOR ~ R E ~ A ~ A ~ ~ @ ~  
inisator of the National Aero- 
% with respect to an 
sant, and Richard A. 
nautics and Space A d d  
i ~ ~ e ~ ~ o ~  of William R. 
bQth Qf ~ Q ~ ~ ~ ~ ~ S  
wing. Filed Aug. 26, 1966, Ser. No. 579,930 
~ m. @#. c m  7~10 ,7 /12 ;  co7a 31/20 
purity product suitable for polymer snythesis is obtained. 2o C&Q C BHQ 
C1--$i-C1+ 4c  0 I 55NH2 --t CeHeNH-Si-NHCeHa I + 2CeHaNHzHCl 
formance of work under a NASA contract and is sub- This reaction does not go to completion, however, and 
ject to the provisions of Section 305 of the National Aero- 25 the by-product aniline hydrochloride reacts with the prod- 
nautics and Space Act of 1958, Public Law 85-568 (72 uct to produce side-reaction vroducts such as anilinodi- 
The invention described herein was made in the per- ABHS A@€€& 
Stat. 435; 42 US.C. 4257). 
This invention relates to the synthesis of dianifino- 
silanes. 
Dianilinosilanes are useful for the preparation of an 
outstanding new class of silicon-containing polymers. 
These polyaryloxysilane polymers, exemplified by a struc- 
ture having the formula 
offer properties suitable for use as thermoplastic, thermo- 
setting or elastomeric material for various applications 
in the aerospace field, for example, as a protective coat- 
ing, as well as in other fields. In particular the polyaryl- 
oxysilane polymers exhibit a high degree of thermal sa- 
bility and good mechanical properties. 
These polymers are prepared by condensation of a di- 
anilinosilane such as dianilinodiphenylsilane with an or- 
ganic diol such as p,p-biphenol. The most crucial feiature 
of this synthesis is the use of a dianilinosilane reactant 
having a high degree of purity. The molecular weight and 
mechanical properties of the polymers are highly sensi- 
tive to the presence of impurities in this reactant, and 
the polymer properties obtained using an impure diani- 
Iinosilane are not sufficiently reproducible for practical 
applications. 
~Dianilinodiphenylsilane has been prepared previously 
by reaction of diphenyldichlorosilane with aniline in ben- 
zene, the product being recovered by fractional crystal- 
lization. The properties 5f the product in this procedure 
have been erratic. Melting points as low as 151" C. and 
as high as 161" C. have been reported, indicating a lack 
of reproducibility and the presence of impurities. In ad- 
dition the yield is low, less than 50% being obtained in 
most cases. I t  is thus apparent that this procedure would 
not be suitable for large-scale preparation of the diani- 
linosilane reactant for polymer synthesis. 
phenylchlorosilane. The amount of such side-products 
formed in the reaction mixture is extremely sensitse to 
minor variations in temperature, reaction time and other 
30 conditions. Such side reactions are enhanced 'by the fact 
that the aniline hydrochloride salt is soluble in moet sol- 
vents in the presence of aniline. 
The present reaction in the presence of s-collidine is 
postulated to proceed as follows: 
%%- 
I, 
\ 
I" 
2% s- 
x 
40 
U 
CuHa 
I 
CUH~NH-S~-NHCUH~ + 2HC1. 
C Hs 
baHa 
45 
The s-mllidine is a stronger base than aniline and acts as 
a preferential acceptor for the hydrochloric acid produced 
in the reaction system. In addition, the s-collidine hydro- 
chloride has a very low solubility in the solvents em- 
50 ployed, and this compound may be less able, for steric 
reasons, to react with the silane product to produce un- 
desirable side-reaction products. 
The dichlorosilane reactant in the present process is 
represented by the formula 
R 
I 
Cl-S1-C1 
I 
R' 
55 
6o where R and R' are methyl, phenyl or vinyl radicals. Ex- 
amples of specific reactants included are diphenyldichlo- 
rosilane, dimethyldichlorosilane, methylphenyldichloro- 
silane and methyIvinyldichlorosilane. 
The present process is carried out by mixing the dichlo- 
65 rosilane, aniline and s-dlidine in a suitable solvent. As 
indicated by the equation given above, a ratio of two 
moles aniline per miole silane is used. Excess aniline is to 
be avoided since side reactions might be enhanced. To 
ensure that all of the HCI is taken up rapidly, a molar 
r0 excess of s-collidine is employed, an excess of about 50% 
being preferred. 
The organic solvent for this process can be any solvent 
3,433,818 
4 
in which the reactants and product, but not the s-collidine 
hydrochloride salt, are soluble and which is inert to  the 
readon.  Examples ,of suitable solvents include tetra- 
hydrofuran, benzene, and petroleum ether, with tetra- 
hydrofuran being preferred. The amount of solvent is not 
critical except that enough should be provided to main- 
tetrahydrofuran was added over a period of one hour to 
a stirred mixture of 211 grams of distilled aniline and 
596 grams of 2,4,6-trimethylpyridine. After all the silane 
mixture was added, 400 milliliters of dry tetrahydrofuran 
was added, and stirring was continued for one hour. 
The resulting mixture was filtered to give 318 grams of 
tain the reactants and the product in solution. 
Although the reaction temperature is not critical, a 
temperature of about 25" to 60" C. is preferred. The re- 
action proceeds readily at room temperature, heat being 
liberated when the reactants first come into contact. To 
avoid over-heating it is preferred to add the dichloro- 
silane gradually to a mixture of the remaining reactants. 
A period of about one to three hours is required for 
completion of the reaction. In order to avoid degradation 
of the product, the reaction is conducted in the substan- 
tial absence of moisture, preferably by providing a dry 
nitrogen atmosphere over the reaction mixture. As a fur- 
ther urecaution the solvents used in the reaction and sub- 
sequent recovery steps should be dried prior to use. 
The dianilinosilane produced by this reaction is in 
solution in the reaction medium, the by-product s-collidine 
hydrochloride forming an insoluble precipitate. This pre- 
cipitate is readily removed by means such as filtration to 
allow recovery of the product. The product dianilinosil- 25 
anes can be recovered from solution by crystallization 
from solvents such as benzene, petroleum ether or pe- 
troleum naphtha. A particularly suitable solvent for this 
purpose is the high-flash petroleum naphtha having the 
following properties: distillation temperature range at 30 
760 mm, Rg, 122 to 136" C.; specific gravity, 0.763; Kauri 
butaslo1 value, 39.9 cc.; aniline point, 122.5" F.; and flash 
point,59" F. This solvent is available commercially under 
the tradename "Super Naphtholite." In a preferred pro- 
cedurp the solution containing the dianilinosilane is first 35 
subjected to flash evaporation to remove the bulk of the 
s~lvent, and the crystallizing solvent is added to the hot 
concentrate obtained by the flash evaporation at a pro- 
portion of about four parts by weight per part dianilino- 
silane. The resulting solution is then cooled to crystallize 40 
the dianilinosilane. In order to remove the small amounts 
of impurities which are formed in this process the crystal- 
lized product is then washed with chloroform, which 
readily dissolves the impurities. The product is also slight- 
ly soluble in chloroform so that a minimum amount of 45 
chloroform, a short contact time of less than thirty 
minutes and a temperature below 30" C. are preferably 
used to avoid unduly decreasing the yield. 
In the preparation of dianilinodiphenylsilane, the prod- 
uct also can be recovered from the solution remaining 50 
after removal of the s-collidine hydrochloride by vacuum 
distillation, the product being removed in the fraction 
which boils at 250 to 260" C. This method is not recom- 
mended for large-scale use because thermal degradation 
of the product may occur. 
The dianilinosilanes produced by this process have a 
reproducible high purity over 99%, and are suitable for 
use in preparation of polyaryloxysilane polymers. The 
products are crystalline solids melting at 166"-167" C. 
and 63.0"-63.5" C., respectively, for dianilinodiphenyl- 6o 
silane and dianilinodimethylsilane. The presence of sig- 
nificant amounts of impurities is indicated by coloration 
and by a decrease in melting point. Yields of product ob- 
tained in this process are up to 80%1 to 85%. 
conditions to avoid degradation prior to use. The use of 
a dry nitrogen atmosphere in storage is suitable for this 
purpose. 
The invention is further illustrated by the following 
eramples. 70 
20 
55 
The product dianilinosilanes should be stored under dry 65 
EXAMPLE I 
Dianilinodiphenylsilane was prepared on a laboratory 
scale by the following procedure. A mixture of 253.2 
grams of diphenyldichlorosilane in 50 milliliters of dry 75 
2,4,6-trimet&lpyridine hydrochloride. The filter cake was 
washed twice with tetrahydrofuran and the combined 
filtrates were reduced by evaporation until a cream- 
colored paste was obtained. Petroelum ether was added 
to the paste and the solid was separated by filtration. The 
filtrate was cooled in a Dry Ice-acetone bath and then 
filtered. The combined filter cakes were dissolved in a 
minimum amount of hot, dry tetrahydrofuran and then 
5 cooled and diluted with petroleum ether. The mixture 
was then cooled in a Dry Ice-acetone bath and filtered. 
The solid product was dried in a vacuum over for 18 
hours. The dried product weighed 292.5 grams (80,3% 
yield) and had a melting pointof 166" to 168" C. 
Dianilinodiphenylsilane prepared by this procedure, but 
in the absence of s-collidine, was obtained at yields of only 
40% to 50%, and the product purity was low as evidenced 
by lower melting points, typically 162" to 163". 
EXAMPLE I1 
Dianilinodimethylsilane was prepared in a I-liter, 3- 
necked flask equipped with a Trubore stirrer, reflux con- 
denser with a drying tube affixed, and a dropping fun- 
nel. The apparatus was flame-dried and then swept with 
nitrogen until cool. A solution of 38.7 g. (0.30 mole) of 
dimethyldichlorosilane in 100 ml. of petroleum ether 
(30-60" C.) was placed in the dropping funnel, and 55.9 
g. (0.60 mole) of freshly distilled aniline and 109.1 g, 
(0.90 mole) of s-collidine were mixed with 400 nil. of 
petroleum ether in the reaction flask. The aniline/s-colli- 
dine solution was heated to reflux on a steam bath and 
the dimethyldichlorosilane solution was added dropwise 
over a period of one hour while the reaction mixture 
was stirred rapidly. The resulting thick white slurry was 
held at the reflux temperature while being stirred for one 
additional hour, and was then cooled slowly @ about 30" 
C. The warm slurry was filtered with suction on a sintered 
glass funnel and the filter cake was washed with warm 
petroleum ether. The dried filter cake, consisting of s-col- 
lidine hydrochloride, weighed 93.0 g. (98 peraent of theo- 
retical). Thr: combined petroleum ether filtrates were 
evaporated to a yellow viscous liquid by using a rotary 
evaporator at reduced pressure. The viscous yellow resi- 
due was dissolved in 1100 ml. of warm 30-60" C. petro- 
leum ether and allowed to stand at 23" C. for 18 hours, 
A 50.0 g. crop (about 70 percent yield) of yellow crys- 
tals, melting point 57-59' C., was obtained, Three crys- 
tallizations from petroleum ether provided 43 .O grams 
(60 percent yield) of pure white, crystalline dianilinodi- 
metbylsilane, melting point 63.0-63.5' C . 
AigzZysis,-Calculated for C14HI8SiN2: C, 69.36; H, 
7.49; N, 11.56. Found: C, 69.23; H,  7.60; N, 11.44. 
EXAMPLE 111 
A series of pilot-scale syntheses of dianilinodiphenyl- 
silane was carried out in a ten-gallon stairjless steel re- 
actor equipped with a double-anchor stirring blade, The 
reactor was provided with a jacket for heating and cool- 
ing and means for maintaining a dry nitrogen atmosphere. 
Six runs were made using the following amounts of re- 
actants: diphenyldichlorosilane, 4,702 grams; aniline, 
3,636 grams; s-collidine, 11,100 grams; and tetrahydro- 
furan solvent, 2.4 gallons. In each run the aniline, s-col- 
lidine and solvent were placed in the reactor and stirred 
under a nitrogen atmosphere. The diphenyldichlorosilane 
was then added in 1,000 milliliter portions at 15 minute 
intervals. The reaction mixture was stirred and held at a 
temperature of 60" C .  for 4 to 5 hours. The mixture was 
then cooled to room temperature and filtered. The filter 
cakes were washed with tetrahydrofuran at room tem- 
3,433,818 
perature. The combined filtrates were evaporated in a 
Lnwa P46 evaporator to one-third the original volume, 
and the resulting concentrates were diluted while hot 
with equal volumes of the high-flash petroleum naphtha 
available commercially as "Super Naphtholite." The lat- 
ter treatment caused the dianilinosilane to crystallize as 
small, loose, cream-colored crystals. After standing over- 
night, the mixtures were filtered and the crystalhe prod- 
uct was washed once with the high-flash petroleum naph- 
tha and once with chloroform. The resulting slurries were 
filtered to give white crystalline material. The product was 
then dried at 60" C. under a stream of nitrogen. A color- 
less, crystalline material having a meltiiig point of 166"- 
167" C. was obtained at a yield of 60% to 65% in each 
case. These runs demonstrate that dianilinosilanes can be 
prepared reproducibly on a large scale by the process of 
this invention. 
The above examples are merely illustrative and are 
not to be understood as limiting the scope of the inven- 
tion, which is limited only as indicated by the appended 
claims. Furthermore, it is to be understood that numerous 
modifications and changes may be employed by one 
skilled in the art withont departing from the scope of the 
invention. 
What is claimed is: 
1. The process of preparing a dianilinosilane which 
comprises reacting a dichlorosilane having the formula 
R 
I 
Cl-Si-Cl 
I 
R' 
where R is a methyl, a vinyl, or a phenyl radical and R' 
is a methyl, a vinyl, or a phenyl radical with aniline in 
the presence of 2,4,6-trimethylpyridine in an inert or- 
6 
I O  
16 
20 
25 
30 
ganic solvent, separting th resulting precipitated 2,4,6- 
trimethylpyridine hydrochloride from the remaining soh- 
tion and recovering the resulting dianilinosilane from said 
remaining solution. 
2. The process of claim 1 wherein the molar ratio of 
aniline to dichlorosilane is about 2: 1. 
3. The process of claim 2 wherein the molar ratio of 
2,4,6 - trimethylpyridine to dichlorosilane is in excess 
of 1:l. 
4. The process of claim 3 wherein the resulting di- 
anilinosilane is recovered by crystallization from benzene, 
petroleum ether or high-flash petroleum naphtha. 
5. The process of claim 4 wherein the resulting di- 
anilinosilane is washed in chloroform. 
6. The process of claim 1 wherein said inert organic 
solvent is tetrahydrofuran. 
7. The process of claim 1 wherein said dichlorosilane 
is diphenyldichlorosilane. 
8. The process of claim 1 wherein said dichlorosilane 
is dimethjIldichlorosilaiie. 
eferences Cite 
UNITED STATES PATENTS 
2,579,418 12/1951 Cheronis _ _ _ _ _ _  260-448.2 XR 
3,007,886 1111961 Parker _ _ _ _ _ _ _ _  260-448.2 XR 
3,036,019 5/1962 Molotsky et al. _ _  2 6 0 4 4 8 . 2  XR 
3,072,594 111953 Shultz et al. _ _ _ _  2 6 0 4 4 8 . 2  XR 
3,143,514 8/1964 Boyer _ _ _ _ _ _ _ _  2 6 0 4 4 8 . 2  XR 
TOBIAS E. LEVOW, Primary Examiner. 
J. P. PODGORSKI, Assistant Examiner. 
260-2, 46.5, 448.8 
US. C1. X.R. 


Process for preparation of dianilinosilanes Patent

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