Process for decomposing siloxane bond-containing compound

The present invention relates to a novel process for decomposing siloxane bond-containing compound by an alkali decomposer characterized in that one or more selected from a group consisting of secondary and tertiary aliphatic alcohols are used as a decomposition facilitator, and if desired, the decomposition product is further sonicated and treated with a triorganylhalosilane.

TECHNICAL FIELD 
The present invention relates to a novel process for decomposing siloxane 
bond-containing compound by an alkali decomposer characterized in that one 
or more selected from a group consisting of secondary and tertiary 
aliphatic alcohols are used as a decomposition facilitator, and if 
desired, the decomposition product is further sonicated and treated with a 
terminator. 
BACKGROUND ART 
Silixane bond-containing compounds include polyorganosiloxanes, such as for 
example, silicone resin, silicone rubber, etc. A good deal of the siloxane 
bond-containing compound is conventionally discarded in the form of waste 
matters due to the combination failure during processing step, scraps 
formed in finishing step, or useless materials from a variety of 
industrial areas. Such a discarded silicone resin or silicone rubber can 
hardly be re-used because it's reclamation is almost impossible. 
Furthermore, since there have not developed as yet any effective cleavage 
methods for the discarded silicone resin and rubber, they are usually left 
untreated. Accordingly, processing factories have great difficulties to 
treat the wastes. 
Chemical cleavage methods for siloxane bond-containing compound include 
decompositions by heat, acid, or alkali. Among those methods, a process 
for producing alkali metal trimethylsilanolate by heating 
hexamethyldisiloxane in the presence of an alkali metal hydroxide or 
alkoxide, as depicted in the following reaction scheme 1, can be 
exemplified as a related one to the process according to the present 
invention (see, J. F. Hyde et al, J Am. chem. Soc., 75, 5615, 1953; W. S. 
Tatlock and E. G. Rochow, J. Am. Chem. Soc., 72, 528, 1950). 
Reaction Scheme 1 
EQU (CH.sub.3).sub.3 Si!.sub.2 O+ROM.revreaction.(CH.sub.3).sub.3 
SiOM+(CH.sub.3).sub.3 SiOR 
in which 
R represents hydrogen atom or alkyl, and 
M represents Na, K or Li. 
In addition, as depicted in the following reaction scheme 2, a process 
wherein potassium or sodium siloxanediolate is produced through the 
cleavage of cyclodiorganylsiloxane or straight polydiorganylsiloxane 
having a high molecular weight by potassium hydroxide or sodium hydroxide 
in the presence of a primary alcohol such as methanol, ethanol, etc. is 
disclosed in T. Takiguchi and M. Skural, Kogyo Kagaku Zassi, 63, 1476, 
1960; W. Noll, Chemie und Technologie der Silicone, Verlag Chemie, 
Weinheim, 1968; A. Stock and C. Somieski, Ber., 52, 595, 1919; J. F. Hyde, 
J. Am. Chem. Soc., 75, 2166, 1953; and K. A. Andrianov and M. A. 
Sipyagina, Izv. Akad. Nauk SSSR, Neorg. Mat., 4, 2016, 1968. 
##STR1## 
in which M represents Na or K, and 
R' represents methyl or ethyl. 
In the alkali-decomposition method as mentioned above, however, it is 
difficult to control the reaction since a primary alcohol such as 
methanol, ethanol, etc. is used as a decomposition facilitator. Also, 
according to this method, silica combined as a filler may not efficiently 
be recovered; the cleavage yield is low; and the molecular weight of the 
decomposition product is high. 
It is described in the above alkali-decomposition method that secondary or 
tertiary alcohols can be used during the cleavage in addition to primary 
alcohols. However, since it is also described therein that "Secondary 
alcohols react with siloxanes in the presence of KOH or ROK more slowly 
than do primary alcohols, while tertiary alcohols are completely 
unreactive", the technical concept of the existing alkali-decomposition 
method is quite different from that of the present invention. 
DISCLOSURE OF INVENTION 
Under such technical circumstances, the present inventors have extensively 
studied to develop an efficient decomposition method for siloxane 
bond-containing compound, such as for example, silicone rubber, silicone 
resin, silica, etc. which are recently discarded as wastes in a great 
amount. As a result, we have identified that such a purpose can be 
effectively achieved if one or more selected from a group consisting of 
secondary and tertiary aliphatic alcohols are used as a decomposition 
facilitator, and thus completed the present invention. Further, the 
present inventors have found during the studies that the decomposition 
product thus obtained may be sonicated and then treated with a terminator 
in the presence of a decomposer and decomposition facilitator to prepare a 
decomposition product having a lower molecular weight or a less particle 
diameter. Therefore, such an additional process is also included in the 
scope of the present invention. 
Therefore, the present invention provides a process for decomposing 
siloxane bond-containing compound by an alkali decomposer characterized in 
that one or more selected from a group consisting of secondary and 
tertiary aliphatic alcohols are used as a decomposition facilitator. 
The present invention also provides a process for decomposing siloxane 
bond-containing compound characterized in that the siloxane 
bond-containing compound is decomposed by an alkali decomposer in the 
presence of one or more selected from a group consisting of secondary and 
tertiary aliphatic alcohols are used as a decomposition facilitator and 
then the decomposition product is sonicated and treated with a terminator 
after the decomposer and the decomposition facilitator are introduced into 
the reaction system. 
The present invention will be specifically explained in the following.

BEST MODE FOR CARRYING OUT THE INVENTION 
As mentioned above, it is known that secondary or tertiary alcohols can be 
added in the decomposition process of siloxane bond by alkali. However, 
the present inventors have found the astonishing fact that secondary 
and/or tertiary alcohols can still more effectively facilitate the 
cleavage of siloxane bond than do primary alcohols, which is a quite 
different understanding from the earlier one. The present invention is 
based on such an unexpected discovery. 
As the secondary or tertiary alcohol which is used as a decomposition 
facilitator in the present invention, C.sub.1 -C.sub.10 aliphatic alcohols 
having a boiling point of 130.degree. C. or less, such as for example, 
isopropanol, 2-butanol, 2-methyl-2-propanol, 2-pentanol, 3-pentanol, 
2-methyl-2-butanol, t-amyl alcohol, etc. can be mentioned. In the present 
invention, a decomposition facilitator having a boiling point of 
130.degree. C. or less is used because the decomposition product can be 
more conveniently recovered. For the other chemicals used in the present 
invention, it is desirable to use those having a boiling point of 
130.degree. C. or less with the same reason. When a mixture of secondary 
and tertiary aliphatic alcohols is used, the secondary alcohol is 
conventionally used in an amount of 1 to 10 times by volume with respect 
to the tertiary alcohol. 
If desired, in addition to the use of secondary and/or tertiary aliphatic 
alcohols, C.sub.1 -C.sub.10 primary aliphatic alcohol or C.sub.6 -C.sub.10 
alkyl, each of which has a boiling point of 130.degree. C. or less, may be 
used. In the present invention, the primary aliphatic alcohol dilutes the 
reaction solution which usually has a quite high viscosity into a solution 
of an appropriate viscosity, whereby helps the reaction to be proceeded 
without any problem. The alkyl acts as a diluent and also may act as a 
swelling agent to exert a positive influence upon the reaction. 
The primary aliphatic alcohol which can be used in the present invention 
includes methanol, ethanol, n-propanol, 1-butanol, neopentyl alcohol, etc. 
It is preferable to use a cheap primary alcohol having a fewer carbon 
atoms. As the C.sub.6 -C.sub.10 alkyl, n-hexane, n-heptane, 2-methyl 
hexane, 3-methyl hexane, 2,3-dimethyl hexane, 2,4-dimethyl hexane, 
n-octane or their structural isomers can be mentioned. 
When the primary aliphatic alcohol is added, it is preferable to control 
the ratio of the primary alcohol with respect to the secondary and/or 
tertiary alcohol to 1:1 to 1:10 by volume. Also, it is good to maintain 
the total amount of the aliphatic alcohols among the reaction solution 
constantly whether the primary aliphatic alcohol is used or not. That is, 
it is usually desirable to control the total amount of the aliphatic 
alcohols with respect to the material to be decomposed to 30 to 300% by 
weight when the siloxane bond-containing compound is polyorganosiloxane 
compound, and it is desirable to control to 300 to 600% by weight when the 
siloxane bond-containing compound is silica. 
The C.sub.6 -C.sub.10 alkyl is preferably used in an amount of 1 to 70% by 
weight with respect to the secondary and/or tertiary aliphatic alcohols. 
However, the amounts of each chemicals can be varied with the kind of 
chemicals, materials to be decomposed, or the reaction conditions, and 
conventionally the prefered amounts are easily determined by a person 
skilled in this art within the above mentioned ranges. 
As the alkali decomposer used in the process according to the present 
invention, alkali metal hydroxide or alkoxide, for example, sodium 
hydroxide, potassium hydroxide, sodium methoxide, potassium methoxide, 
etc. can be mentioned. It is preferable to use the decomposer in an amount 
of 5 to 40% by weight with respect to the polyorganosiloxane compound and 
20 to 150% by weight to the silica. If the decomposer is used in an amount 
of less than the aforementioned range the cleavage reaction may not be 
proceeded smoothly, and if the amount exceeds the range the 
physico-chemical properties of the resulting silica may be deteriorated 
due to the alkali metal silicate formed during the cleavage. 
When siloxane bond-containing compound is decomposed using the decomposer 
and decomposition facilitator as explained above, the desired cleavage 
reaction can be completed by reacting for one hour to 3 days under 
atmospheric pressure or pressurized at temperatures ranging from 
-20.degree. C. to 100.degree. C. The reaction pressure, time and 
temperature can be varied with the kind of materials to be decomposed or 
the degree of decomposition within the above mentioned ranges. Since the 
temperature, pressure and time are complementary to each other, 
temperature and time, for example, may be depended upon the selected 
pressure. The corelation between temperature, pressure and time determined 
by experiments can be exemplified as the following Table 1. 
TABLE 1 
______________________________________ 
1 2 3 4 
______________________________________ 
3.about.20.sub.kg/cm.sup.2 
Atmospheric 
Atmospheric Atmospheric 
Pressure Pressure Pressure 
50.about.100.degree. C. 
50.about.80.degree. C. 
Room Temperature 
-10.about.20.degree. C. 
1.about.5 hours 
4.about.24 hours 
4.about.24 hours 
1.about.3 days 
______________________________________ 
If necessary, it is preferable to stir the reaction solution to facilitate 
the cleavage. Particularly, according to the present invention, a good 
cleavage yield of more than 90% can be obtained by stirring for 1 to 3 
days even if the temperature is as low as -20.degree. C. (see, condition 4 
in Table 1). 
The waste siloxane bond-containing compound which is to be used as a 
material in the decomposition process according to the present invention 
includes discarded silicone rubber, silicone resin and silica. The wastes 
may be used in the form of mass, but they also be finely cut or ground 
into powder before use. Preferably, wastes having 0.5 to 10 mm of particle 
diameter, more preferably, those having 3 mm or less of particle diameter 
are used upon considering the cleavage yield. 
After the cleavage reaction is completed, neutralization and heating were 
proceeded to obtain silicone oil of a low molecular weight and siloxylated 
silica having about 10 to 100 .mu.m of particle diameter. The cleavage 
process for polyorganosiloxane compound and silica are depicted in the 
following reaction schemes 3 and 4, respectively. 
##STR2## 
in which R represents alkali metal or C.sub.1 -C.sub.10 alkyl, 
M represents alkali metal, 
n denotes an integer of 10 to 40, and 
m denotes an integer of 2 to 6. 
The process described in the above reaction scheme 3 will be more 
specifically explained below. The decomposition product I! obtained from 
cleavage reaction is filtered and the residue is washed with polar or 
nonpolar organic solvent. The filtrate and the washings are mixed 
together. After the organic solvent contained in the mixture is removed by 
distillation under reduced pressure, the residue is neutralized by the 
addition of inorganic acid, preferably hydrochloric acid. The organic 
substance in the upper layer is collected and washed with distilled water. 
The solvent contained therein is eliminated by distillation under reduced 
pressure to obtain the compound of formula II! which contains both the 
terminal hydroxy group and siloxane bond. The resulting compound II! is 
heated for 30 minutes to 4 hours at 120 to 170.degree. C. to obtain the 
compound of formula III! as a cyclic decomposition product in which the 
terminal hydroxy group is absent and only the siloxane bond is contained. 
The compound III! is a silicone oil having an average molecular weight of 
300 to 500. On the other hand, siloxylated fine silica (particle diameter 
of about 10 to 100 .mu.m) is obtained by neutralizing, washing and drying 
the residue resulted from filtration. Herein, the "siloxylated silica" 
means that polyorganosiloxane compound is attached to the surface of the 
solid silica. 
##STR3## 
in which R" represents C.sub.1 -C.sub.10 alkyl, 
M represents alkali metal, and 
m denotes an integer of 2 to 6. 
According to the cleavage process as explained above, the siloxane 
bond-containing compound can be decomposed with a good yield under 
conditions of low temperature and atmospheric pressure. If silicone oil 
having a lower molecular weight and minuter silica are desired, however, 
the decomposition product obtained from the above cleavage process should 
be sonicated and treated by a terminator of triorganylhalosilane 
represented by the following formula IV! after an alkali decomposer and a 
decomposition facilitator are introduced into the reaction system. 
##STR4## 
in which R.sub.1, R.sub.2 and R.sub.3 independently of one another 
represent C.sub.1 -C.sub.6 alkyl, or phenyl or vinyl which is optionally 
substituted, and 
X represents halogen, preferably chlorine. 
That is, the present invention also relates to a process for decomposing 
siloxane bond-containing compound characterized in that the siloxane 
bond-containing compound is decomposed by an alkali decomposer in the 
presence of one or more selected from a group consisting of secondary and 
tertiary aliphatic alcohols are used as a decomposition facilitator and 
then the decomposition product is sonicated and treated with a 
triorganylhalosilane of formula IV! after the decomposer and the 
decomposition facilitator are further introduced into the reaction system. 
The latter cleavage process will be more specifically explained below. As 
the material to be treated in the latter process, the decomposition 
product obtained in the former cleavage reaction is used. Time to further 
introduce the decomposer and decomposition facilitator into the 
decomposition product in order to carry out the latter process is not 
restricted, and any appropriate step before or after filtration, or before 
or after neutralization may optionally be selected. 
The decomposers and the decomposition facilitators mentioned for the former 
cleavage reaction can also be used in the latter cleavage process, 
however, it is not necessary to use the same decomposers and decomposition 
facilitators in the latter process as those used in the former process. 
The preferable amounts of decomposer and decomposition facilitator with 
respect to the material are identical to those mentioned for the former 
process. 
Sonication is performed at a temperature of less than room temperature, 
preferably at 0 to 5.degree. C., for 10 to 30 minutes under conditions of 
16 to 30 kHz and 0.5 to 2 kW in the presence of a decomposer and a 
decomposition facilitator. After the sonication is completed, the 
sonication product is treated with the triorganylhalosilane of formula 
IV! as a terminator in an anhydrous nonpolar solvent optionally in the 
presence of an acid. 
As the acid which can be used in the termination reaction, inorganic acid, 
preferably hydrochloric acid, nitric acid or sulfuric acid, particularly 
preferably hydrochloric acid can be mentioned. Any conventional nonpolar 
solvent in the field of organic synthesis can be used in the present 
reaction if it does not adversely affect the reaction. The solvent is used 
in alone or mixed with other one or more solvents. In the present reaction 
system, anhydrous nonpolar solvents should be used because the 
alkoxide(-OR) or the metal oxide(-OM) group present at both terminals of 
the decomposition product may be dissociated into hydroxide and 
subsequently dehydration and condensation reactions may occur in the 
presence of water. As the specific examples for the triorganylhalosilane 
of formula IV!, trialkylhalosilane, dialkylmonophenylhalosilane, 
dialkylmonovinylhalosilane, monoalkyldiphenylhalosilane, 
monoalkyldivinylhalosilane, triphenylhalosilane, 
diphenylmonovinylhalosilane, monophenyldivinylhalosilane or 
alkylphenylvinylhalosilane can be mentioned. Among them, one or more 
selected from a group consisting of trimethylchlorosi lane, 
triethylchlorosi lane, triphenylchlorosilane, dimethylethylchlorosilane, 
diethylmethylchlorosilane, methylvinylphenylchlorosilane, 
ethylvinylchlorosilane, divinylmethylchlorosilane, 
divinylethylchlorosilane and divinylphenylchlorosilane are preferably 
used, and one or more selected from a group consisting of 
trimethylchlorosilane, triethylchlorosilane and triphenylchlorosilane are 
most preferably used. When the acid is used in the termination reaction, 
it can be applied in amounts ranging from 1 to 10 times by volume with 
respect to the triorganyihalosilane according to the purpose. 
It is understood that the decomposition mechanism of polyorganosiloxane 
compound in the latter cleavage process, in which sonication and treatment 
by a terminator are carried out, is proceeded as in the following reaction 
scheme 5. Also, it is thought that the siloxylated silica obtained from 
the former cleavage process may be reacted with the triorganylhalosilane 
as in the following reaction scheme 6. If the siloxylated silica is 
treated with an acid such as hydrochloric acid instead of the 
triorganylhalosilane in reaction scheme 6, hydroxy groups remain at both 
terminals. 
##STR5## 
in which R" represents C.sub.1 -C.sub.10 alkyl. 
##STR6## 
in which R" represents C.sub.1 -C.sub.10 alkyl, 
M represents alkali metal, and 
m denotes an integer of 2 to 6. 
After the latter cleavage reaction is completed, conventional work-up 
processes such as filtration, centrifugation, distillation under reduced 
pressure, etc. may be carried out to obtain the desired oily compound 
which has a variety of polymerization degree and contains terminal hydroxy 
groups and siloxane bonds. This silicone oil may be recovered as it is or 
may be heated for 30 minutes to 4 hours at 120 to 170.degree. C. to 
recover a silicone oil which has an average molecular weight of 150 to 300 
and in which terminal hydroxy groups are absent and siloxane bonds are 
retained. While, it is possible to obtain still more micronized 
siloxylated silica (particle diameter of less than 1 .mu.m) than the 
silica obtained from the former cleavage process if the solid residue 
obtained through the latter cleavage reaction, washing with distilled 
water, filtration, centrifugation, etc. is dried under reduced or 
atmospheric pressure at temperatures ranging from 100 to 110.degree. C. 
In the latter cleavage process, the product resulted from the first 
sonication may be sonicated secondarily in the presence of a terminator. 
Whether or not the secondary sonication is performed depends on the 
materials used or reaction conditions, and it can be easily determined by 
a person skilled in this art. 
As explained above, the present invention has some characteristics such 
that secondary and/or tertiary aliphatic alcohols are used as a 
decomposition facilitator in the process for decomposing siloxane 
bond-containing compound by alkali decomposer, and that the decomposition 
product is sonicated and treated with a terminator in the optional 
subsequent process. Due to its unique constitutional characteristics, the 
present invention exhibits a superior effect in cleavage rate and yield to 
that of the existing cleavage processes by alkali. 
The process for decomposition according to the present invention can be 
applied to a rubber composition prepared by combining synthetic rubber and 
polyorganosiloxane compound. The silicone oil obtained from the 
decomposition can be advantageously used in the preparation of silicone 
rubber, insulating oil, lubricating oil having a low viscosity, engine 
oil, modifier having a high molecular weight, fiber processing agent, 
water repellent, additive for cosmetics, varnish, parting agent, surface 
treatment, vacuum pump oil, functional treatment, pinch-off oil, gloss 
agent, etc. The siloxylated silica can be effectively used as reinforcing 
filler for various rubbers including silicone rubber, developing agent of 
agricultural chemicals, pigment, anti-precipitating agent for printing 
ink, gloss-removing agent, additive for cosmetics, etc. 
The present invention will be more specifically explained by the following 
examples. However, it should be understood that the examples are intended 
to illustrate but not to in any manner limit the scope of the present 
invention. Unless otherwise stated, aliphatic alcohols having a purity of 
98% or more are used in the following examples. 
Reference Example 1 
100 ml of octamethylcyclotetrasiloxane, 5 ml of tetramethylammonium 
hydroxide(CH.sub.3).sub.4 NOH! and 50 ml of benzene were introduced into 
a reaction flask equipped with a refluxing condenser, a stirrer and a 
thermometer, and the reaction mixture was heated for 5 hours at 
100.degree. C. Tetrarnethylammonium hydroxide was removed again by heating 
the mixture at 130.degree. C. to prepare 70 g of crude silicone rubber 
having a molecular weight of 15,000 or more. 50 g of fumed silica having 
an average particle diameter of 73.72 .mu.m (diameter range: about 10 to 
500 .mu.m, specific surface area: 0.1137 m.sup.2 /gm, see FIG. 1) was 
combined with 50 g of the crude silicone rubber thus obtained. A mixture 
of 1 g of benzoyl peroxide, 5 ml of octamethylcyclotetrasiloxane and 20 ml 
of diethylether was added thereto and then the whole mixture was matured 
in a refrigerator of 5 to 10.degree. C. Then, the silicone rubber thus 
produced was vulcanized by heating for 2 hours at 170.degree. C. and 
200.degree. C., respectively. This vulcanized silicone rubber was used as 
a material in the following examples. 
EXAMPLE 1 
(a) Cleavage of silicone rubber and recovery of silicone oil 
100 g of the silicone rubber prepared in Reference Example 1 was introduced 
into an autoclave equipped with a stirrer, a mixture of 100 ml of 
isopropanol and 100 ml of methanol was added thereto and then the reaction 
mixture was stirred for 30 minutes. After 15 g (0.37 mole) of sodium 
hydroxide was added to the reaction mixture, the autoclave was sealed. The 
mixture contained in the autoclave was stirred for 2 hours under 
conditions of inner pressure 6.+-.2 kg/cm.sup.2 and temperature 
60.+-.10.degree. C. in order to carry out the cleavage reaction. Then, the 
reaction solution was cooled down to room temperature, the decomposition 
product was filtered by suction and the resulting residue was washed with 
n-hexane 5 times. The filtrate and the washings were combined and then 
n-hexane, isopropanol and methanol contained therein were removed under 
reduced pressure in a rotary evaporator. The residue was cooled down to 
room temperature, introduced into a separatory funnel and then neutralized 
with 5N aqueous hydrochloric acid solution. The organic substance in the 
upper layer was thoroughly washed with distilled water and dried over 
anhydrous sodium sulfate. Then, the organic solvent remained was 
eliminated under reduced pressure at a temperature of 50.degree. C. or 
less. Since the resulting residue contained terminal hydroxy groups and 
siloxane bonds (see, IR absorption spectrum of FIG. 2), it was heated for 
3 hours at 150.degree. C. under atmospheric pressure to obtain 45 g (Yield 
90%; this is a decomposition yield with respect to the weight of silicone 
rubber and the following yields should be understood equally) of silicone 
oil in which the terminal hydroxy groups were absent and siloxane bonds 
were contained (see, FIG. 3). 
(b) Recovery of siloxylated silica powder 
The residue obtained after filtration in (a) was washed with n-hexane 5 
times, neutralized with 5N aqueous hydrochloric acid solution and then 
washed with distilled water 5 times. The washed residue was dried under 
reduced pressure at 50.degree. C. to obtain powder which was identified by 
IR analysis to have hydroxy groups and siloxane groups attached to the 
surface thereof (see, FIG. 4). This powder sample was dried for 2 hours at 
120.degree. C. to obtain 52 g of silica which was identified by IR 
analysis to have siloxane groups only on the surface thereof and hydroxy 
groups were eliminated therefrom(see, FIG. 5). The siloxylated silica thus 
obtained was analyzed by the method as represented below, and as a result 
it was identified to have an average particle diameter of 87.40 .mu.m 
(diameter range: 1.6.about.600 .mu.m, specific surface area: 0.2697 
m.sup.2 /gm, see FIG. 6). 
Conditions for Analysis of Particle Size 
Instrument: Mastersizer X (Malvern Instruments Co., England) 
Principles: laser diffraction using Mie theory, light scattering and back 
scattering 
Dispersing Medium: distilled water 
Detector: single chip silicon photodiode array (multi element detector: 31 
channel) 
Wavelength: He--Ne laser, wavelength 632.8 nm, 5 mW 
Procedure: Specific amount of sample is dispersed in distilled water, 
stirred for 30 minutes and simultaneously sonicated (36 kHz, 60 watt). 
Then, the sample is analyzed under the above mentioned conditions. 
(c) Molecular Weight Analysis of Silicone oil 
The silicone oil obtained in (a) was subjected to gel filtration 
chromatography under the conditions as mentioned below. The chromatogram 
thus obtained (FIG. 7) was compared with the calibration curve of 
molecular weight marker (FIG. 8), from which it was identified that the 
weight average molecular weight of the silicone oil is 360 (molecular 
weight range: 350.about.400). 
Column: Waters Styragel TM 10 .ANG. and 100 .ANG. combined serially 
Temperature: 25.degree. C. 
Eluent: chloroform 
Detector: UV 245 nm 
Molecular Weight Marker Sample: polystyrene (molecular weight 2000, 1800, 
1000, 600, 400, 300) 
Flow Rate: 1.6 ml/min 
It can be seen from the result of the present example that the amount of 
silicone oil obtained by cleavage reaction is lower than 50 g which is the 
amount of material rubber, and that the amount of silica recovered is 
higher than 50 g which is the amount of fumed silica combined first. It Is 
considered that this is because parts of the decomposition product and the 
material not decomposed, each of which contains siloxane groups and/or 
terminal hydroxy groups, are attached to the surface of the recovered 
silica. Accordingly, the particle size distribution range of the recovered 
silica has been upwardly readjusted a little. 
EXAMPLE 2 
The same procedure as Example 1 was carried out except that methanol was 
not used and instead 200 ml of isopropanol was used alone in the cleavage 
reaction to obtain 40 g (Yield 80%) of silicone oil having an average 
molecular weight of 470 (molecular weight range: 450.about.500) and 55 g 
of siloxylated silica having an average particle diameter of 86.98 .mu.m. 
EXAMPLE 3 
100 g of silicone rubber prepared in Reference Example 1 was finely cut in 
a size of 1 to 3 mm, introduced into a 1 l three necked flask equipped 
with a refluxing condenser and a stirrer and then 300 ml of isopropanol 
and 40 g (1 mole) of sodium hydroxide were added thereto. The mixture was 
stirred for 15 hours under conditions of room temperature and atmospheric 
pressure to decompose the silicone rubber. Then, the decomposition product 
was filtered by suction and the residue thus obtained was washed with 
n-hexane 5 times. The filtrate and the washings by n-hexane were combined 
and then n-hexane and isopropanol contained therein were removed under 
reduced pressure in a rotary evaporator. The residue was introduced into a 
separatory funnel and then neutralized with 5N aqueous hydrochloric acid 
solution. The organic substance in the upper layer was thoroughly washed 
with distilled water and dried over anhydrous sodium sulfate. Then, the 
organic solvent remained was eliminated under reduced pressure. The 
resulting residue was heated for 3 hours at 150.degree. C. under 
atmospheric pressure to obtain 45.2 g (Yield 90.4%) of silicone oil having 
an average molecular weight of 360 (molecular weight range: 350.about.400; 
determined by gel filtration column chromatography) in which the terminal 
hydroxy groups were absent and siloxane bonds were contained. 
The residue obtained after washing with n-hexane(5 times) was treated 
according to the same procedure as Example 1 to prepare 50 g of 
siloxylated silica having an average particle diameter of 87.43 .mu.m. 
EXAMPLE 4 
150 ml of isopropanol, 150 ml of methanol and 15 g (0.375 mole) of sodium 
hydroxide were introduced into a 1 l double neck flask equipped with a 
refluxing condenser and a stirrer and then they were dissolved and cooled 
down to room temperature. 100 g of silicone rubber prepared in Reference 
Example 1 was finely cut in a size of 1 to 3 mm and then added thereto. 
The mixture was stirred for 16 hours to decompose the silicone rubber. The 
decomposition product was filtered by suction and the residue thus 
obtained was washed with a mixture of n-hexane and methanol (1/1, v/v) 5 
times. The filtrate and the washings were combined and then n-hexane, 
isopropanol and methanol contained therein were removed under reduced 
pressure in a rotary evaporator. The residue was cooled down to room 
temperature, introduced into a separatory funnel and then neutralized with 
5N aqueous hydrochloric acid solution. The organic substance in the upper 
layer was thoroughly washed with distilled water 5 times and dried over 
anhydrous sodium sulfate. Then, the organic solvent remained was 
eliminated under reduced pressure. The resulting residue was heated for 3 
hours at 150.degree. C. under atmospheric pressure to obtain 46 g (Yield 
92%) of silicone oil having an average molecular weight of 360 (molecular 
weight range: 350.about.400; determined by gel filtration column 
chromatography) in which the terminal hydroxy groups were absent and 
siloxane bonds were contained. 
The residue obtained after washing with a mixture of n-hexane and methanol 
(5 times) was treated according to the same procedure as Example 1 to 
prepare 51 g of siloxylated silica having an average particle diameter of 
87.13 .mu.m. 
EXAMPLE 5 
The same procedure as Example 4 was carried out except that 20 g (0.357 
mole) of potassium hydroxide instead of sodium hydroxide was used in the 
cleavage reaction and the cleavage time was adjusted to 10 hours to obtain 
46 g (Yield 92%) of silicone oil having an average molecular weight of 360 
(molecular weight range: 350.about.400) and 51 g of siloxylated silica 
having an average particle diameter of 87.36 .mu.m. 
EXAMPLE 6 
The same procedure as Example 4 was carried out except that 100 ml of 
n-hexane was additionally used in the cleavage reaction and the cleavage 
time was adjusted to 13 hours to obtain 45 g (Yield 90%) of silicone oil 
having an average molecular weight of 360 (molecular weight range: 
350.about.400) and 52 g of siloxylated silica having an average particle 
diameter of 87.59 .mu.m. 
EXAMPLE 7 
The same procedure as Example 6 was carried out except that 20 g (0.357 
mole) of potassium hydroxide instead of sodium hydroxide was used in the 
cleavage reaction and the cleavage time was adjusted to 8 hours to obtain 
46 g (Yield 92%) of silicone oil having an average molecular weight of 370 
(molecular weight range: 350.about.400) and 51 g of siloxylated silica 
having an average particle diameter of 87.45 .mu.m. 
EXAMPLE 8 
The same procedure as Example 6 was carried out except that 7 g (0.125 
mole) of potassium hydroxide was used together with 10 g (0.25 mole) of 
sodium hydroxide in the cleavage reaction and the cleavage time was 
adjusted to 6 hours to obtain 47 g (Yield 94%) of silicone oil having an 
average molecular weight of 360 (molecular weight range: 350.about.400) 
and 50 g of siloxylated silica having an average particle diameter of 
87.39 .mu.m. 
EXAMPLE 9 
The same procedure as Example 8 was carried out except that 150 ml of 
2-butanol was used instead of isopropanol in the cleavage reaction and the 
cleavage time was adjusted to 7 hours to obtain 46 g (Yield 92%) of 
silicone oil having an average molecular weight of 360 (molecular weight 
range: 350.about.400) and 51 g of siloxylated silica having an average 
particle diameter of 87.49 .mu.m. 
EXAMPLE 10 
50 g of the residue obtained before the neutralization with 5N aqueous 
hydrochloric acid solution in Example 4 was introduced into a 1 l plastic 
beaker and then a mixture of 20 g (0.5 mole) of sodium hydroxide, 150 ml 
of isopropanol and 100 ml of methanol was added thereto. The reaction 
mixture was sonicated for 10 minutes under conditions of 20 kHz and 1 kW 
while the temperature was maintained to 0 to 5.degree. C. The reaction 
solution sonicated was treated with 40 ml of trimethylchlorosilane and 100 
ml of dry diethylether. The whole mixture was introduced into a separatory 
funnel, thoroughly washed with distilled water and then the organic layer 
was separated. After the organic solvent contained therein was removed by 
distillation under reduced pressure, the residue was heated for 3 hours at 
150.degree. C. to obtain 70 g of silicone oil having an average molecular 
weight of 280 (molecular weight range: 150.about.300) 
EXAMPLE 11 
50 g of the residue obtained after washing with a mixture of n-hexane and 
methanol in Example 4 was introduced into a 200 ml plastic beaker and then 
10 g (0.178 mole) of potassium hydroxide and 100 ml of isopropanol were 
added thereto. The reaction mixture was sonicated for 20 minutes under 
conditions of 20 kHz and 1 kW while the temperature was maintained to 0 to 
5.degree. C. A mixture of 30 ml of trimethylchlorosilane and 50 ml of dry 
diethylether was added to the reaction solution sonicated and then the 
resulting mixture was sonicated for further one minute under the same 
conditions. The mixture was thoroughly washed with distilled water and 
then centrifuged for 6 minutes at 17,400.times.g to collect the 
precipitate. The precipitate was dried for one day in an oven of 
105.degree. C. to obtain 41 g of siloxylated solid silica powder. This 
siloxylated silica was analyzed according to the same procedure as Example 
1 to have an average particle diameter of 0.38 .mu.m (diameter range: 
0.10.about.1.25 .mu.m, specific surface area: 7.5055 m.sup.2 /gm, see FIG. 
9). 
EXAMPLE 12 
The same procedure as Example 11 was carried out except that a mixture of 
trimetliylchlorosilane and hydrochloric acid (4/1, v/v) was used instead 
of trimethylchlorosilane to obtain 41 g of siloxylated solid silica powder 
having an average particle diameter of 0.44 .mu.m (diameter range: 
0.10.about.1.50 .mu.m, specific surface area: 6.3250 m.sup.2 /gm, see FIG. 
10). 
EXAMPLE 13 
100 g of the decomposition product obtained before the filtration in 
Example 4 was introduced into a 1 l plastic beaker and then 20 g (0.36 
mole) of potassium hydroxide and 50 ml of isopropanol were added thereto. 
The reaction mixture was sonicated for 20 minutes under conditions of 20 
kHz and 1 kW while the temperature was maintained to 0 to 5.degree. C. The 
reaction solution sonicated was centrifuged for 6 minutes at 
17,400.times.g to collect the supernatant. The supernatant was neutralized 
by 5N aqueous hydrochloric acid solution, washed with distilled water, 
dried, distilled under reduced pressure to remove the organic solvent and 
heated for 3 hours at 150.degree. C. according to the same procedure as 
Example 1 except that 100 ml of n-hexane was added to obtain 45 g (Yield 
90%) of silicone oil having an average molecular weight of 360 (molecular 
weight range: 350.about.500). 
The precipitate obtained after centrifugation was treated according to the 
same procedure as Example 11 to prepare 11 g of siloxylated solid silica 
powder having an average particle diameter of 0.77 .mu.m (diameter range: 
0.1.about.3.0 .mu.m, specific surface area: 4.103 m.sup.2 /gm, see FIG. 
11). 
EXAMPLE 14 
The following experiment was carried out to identify whether the surface of 
silica which is not ground is siloxylated or not when the silica is 
treated with the decomposition product obtained in Example 4. 
The decomposition product obtained before filtration in Example 4 was 
introduced into 2 l polyethylene flask and then 100 g of fumed silica 
(see, FIG. 1) which is commonly used as a reinforcing filler for silicone 
rubber, 200 ml of isopropanol and 200 ml of methanol were added thereto. 
The mixture was stirred for 30 minutes in a water bath of 
50.about.60.degree. C. and subsequently refluxed while heating to a 
temperature of 60.degree. C. or more for one hour. The mixture was cooled 
down to room temperature while stirring. The reaction solution was 
filtered by suction to obtain a solid, which is then washed with methanol 
5 times to remove any rubber remained. The solid was neutralized with 5N 
aqueous hydrochloric acid solution and washed with distilled water to 
remove the hydrochloric acid remained. The washed solid was dried for 10 
hours at 105.+-.5.degree. C. and then heated for one hour at 
150.about.170.degree. C. to obtain 151 g of siloxylated silica having an 
average particle diameter of 73 .mu.m (diameter range: 70.about.100 
.mu.m). While, the filtrate and washings with methanol were combined and 
then solvents such as methanol, isopropanol, etc. were removed in a rotary 
evaporator. The residue was cooled down to room temperature, neutralized 
by 5N aqueous hydrochloric acid solution and then washed with distilled 
water to remove the hydrochloric acid remained. 100 ml of n-hexane was 
added thereto and the supernatant (n-hexane layer) was taken. The n-hexane 
contained in the supernatant was removed under reduced pressure and the 
resulting residue was heated for 3 hours at 130.about.150.degree. C. to 
obtain 40 g (Yield 80%) of silicone oil having an average molecular weight 
of 360 (molecular weight range: 350.about.400). 
EXAMPLE 15 
The following experiment was carried out to identify whether the surface of 
ground silica is siloxylated or not when the silica is treated with the 
decomposition product obtained in Example 4. 
Silica was ground and passed through 250 mesh (which is equal to 63 .mu.m, 
average particle diameter 74.33 .mu.m, diameter range 5.about.80 .mu.m, 
see FIG. 12). 100 g (1.66 mole) of the silica thus obtained was introduced 
into a 2 l polyethylene flask and then 300 ml of isopropanol and 200 ml of 
methanol were added thereto. 100 g (2.5 mole) of sodium hydroxide was 
dissolved in said silica mixture carefully in order not to raise the 
temperature while being stirred. The mixture was cooled down to 
0.about.5.degree. C. and sonicated three times, each of which for 20 
minutes, under conditions of 20 kHz and 1 kW. The reaction solution 
sonicated was combined with the filtrate obtained after filtration of the 
decomposition product in Example 4 and then the resulting mixture was 
refluxed for 30 minutes and one hour in a water bath of 
50.about.60.degree. C. and 60.degree. C. or more, respectively, while 
being stirred thoroughly. The reaction solution was cooled down to room 
temperature and centrifuged for 6 minutes at 17,400.times.g to separate 
the supernatant and precipitate. The supernatant was treated according to 
the same procedure for treating the filtrate in Example 4 except that 
trimethylchlorosilane was used as a neutralizing agent to obtain 41 g 
(Yield 82%) of silicone oil having an average molecular weight of 270 
(molecular weight range: 150.about.300). While, the precipitate was 
treated according to the same procedure as Example 1 to obtain 87 g (Yield 
87%) of siloxylated silica powder having an average particle diameter of 
3.24 .mu.m (diameter range: 0.2.about.10.0 .mu.m, specific surface area: 
1.476 m.sup.2 /gm, see FIG. 13). 
It can be seen from the above Examples that the oily or solid decomposition 
products prepared in Examples 10 to 13 in which the latter cleavage 
process was performed, have a lower average molecular weight or particle 
diameter than those of the decomposition products in Examples 1 to 9 in 
which the latter cleavage process was not performed. That is, the silicone 
oil prepared in Example 10 has a molecular weight of 150.about.300, but on 
the other hand the silicone oils in Examples 1 to 9 and 13 have a 
molecular weight of 350 to 500. Also, the silica powders prepared in 
Examples 11 to 13 have an average particle diameter of 0.38.about.0.77 
.mu.m which is much less than 86.98.about.87.59 .mu.m, an average particle 
diameter of the silica powders prepared in Examples 1 to 9. Accordingly, 
it is understood that the sonication and treatment with a terminator have 
a conspicuous effect on raising the decomposition degree. 
In addition, as can be seen from the results of Examples 14 and 15, 
siloxylated silica having a minute particle diameter can be obtained 
efficiently though the cleavage process according to the present invention 
is applied to silica only. 
Hereinafter, the existing processes wherein primary alcohol is used as a 
decomposition facilitator instead of secondary and/or tertiary aliphatic 
alcohol are represented as Comparative Examples for the purpose of 
comparison. 
Comparative Example 1 
The same procedure as Example 1 was carried out except that 300 ml of 
methanol only was used instead of isopropanol to obtain 30 g (Yield 60%) 
of silicone oil having an average molecular weight of 480 (molecular 
weight range: 470.about.500) and 62 g of silica powder having an average 
particle diameter of 130 .mu.m (diameter range: 110.about.170 .mu.m). 
Comparative Example 2 
The same procedure as Example 1 was carried out except that 200 ml of 
ethanol only was used instead of isopropanol to obtain 32 g (Yield 64%) of 
silicone oil having an average molecular weight of 510 (molecular weight 
range: 500.about.520) and 60 g of silica powder having an average particle 
diameter of 150 .mu.m (diameter range: 115.about.185 .mu.m). 
Comparative Example 3 
The same procedure as Example 1 was carried out except that 300 ml of 
methanol only was used instead of isopropanol, 40 g (1 mole) of sodium 
hydroxide was used and the cleavage reaction was carried out for 18 hours 
at 50.about.60.degree. C. under atmospheric pressure to obtain 37 g (Yield 
74%) of silicone oil having an average molecular weight of 420 (molecular 
weight range: 400.about.450) and 55 g of silica powder having an average 
particle diameter of 150 .mu.m (diameter range: 116.about.180.2 .mu.m). 
Comparative Example 4 
The same procedure as Example 1 was carried out except that 300 ml of 
ethanol only was used instead of isopropanol, 40 g (1 mole) of sodium 
hydroxide was used and the cleavage reaction was carried out for 18 hours 
under conditions of room temperature and atmospheric pressure to obtain 36 
g (Yield 72%) of silicone oil having an average molecular weight of 430 
(molecular weight range: 400.about.450) and 55 g of silica powder having 
an average particle diameter of 150 .mu.m (diameter range: 111.about.179 
.mu.m). 
In the above Comparative Examples 1 to 4, alkali metal hydroxide is used as 
a decomposer and primary aliphatic alcohol is used as a decomposition 
facilitator. Accordingly, even if the amount of decomposer or 
decomposition facilitator is increased in the comparative examples, the 
results are inferior to that of the present invention which uses secondary 
and/or tertiary aliphatic alcohols as a decomposition facilitator. That 
is, the comparative examples represent yield of 60 to 74% which are much 
less than the yield of 90% or more according to the present invention. 
Furthermore, when the particle diameter of the decomposed silica is 
considered, the average particle diameter of silica prepared in Examples 1 
to 9 (not sonicated) and Examples 11 to 13 (sonicated) have decreased by 
about half and by about 1/140 to 1/500, respectively, with respect to that 
of silica prepared in comparative examples. 
According to the cleavage process of the present invention, the siloxane 
bond-containing compound can be efficiently decomposed to silicone oil 
having a low molecular weight and siloxyated silica powder having a minute 
particle diameter in a high yield. Particularly, if the latter cleavage 
process wherein the decomposition product prepared in the former cleavage 
process is sonicated and treated by triorganohalosilane in a nonpolar 
solvent is carried out, siloxylated silica powder having an average 
particle diameter of less than 1 .mu.m can be prepared. 
The present invention provides an effective method to convert the discarded 
silicone resin or rubber into a useful material. Therefore, the present 
invention is expected to be used advantageously in the industrial field 
and to have a great value for preventing environmental contamination.