Method for the manufacture of branched polysiloxane

The present invention is a novel method for the manufacture of branched polysiloxanes having the polysiloxane SiO.sub.4/2 unit as the branch center precisely bonded to one end of a diorganopolysiloxane. The present invention concerns a method for the manufacture of a branched polysiloxane characterized by reacting alinear polysiloxane with a reactive polysiloxane having halogen substitution.

BACKGROUND OF INVENTION 
The present invention concerns a method for the manufacture of novel 
branched polysiloxanes, more specifically a method for the manufacture of 
branched polysiloxanes comprised of the polysiloxane unit SiO.sub.4/2 as 
the branch center and a diorganopolysiloxane units as the branch. 
Numerous proposals have been made for polysiloxanes having branches inside 
the molecules and they have been commerically available. For example, in 
W.H. Dickstein et al., Macromolecules, 22, 3886-3888 (1989), is reported 
the synthesis of branched polydimethylsiloxanes with 4 amino- 
group-terminated polydimethylsiloxy groups with controlled molecular 
weight. However, there have not been any reports of organopolysiloxanes 
having the polysiloxane unit SiO.sub.4/2 as the branch center. 
Most of the known branched organopolysiloxanes are simple mixtures or 
reaction products of a SiO.sub.4/2 component and a diorganopolysiloxane 
component, and the structures are not clear. For example, H. Huang et al.: 
Polymer Bulletin, 14, 557-564 (1985) reported polymers obtained by 
reacting hydroxy-terminated dimethylpolysiloxane and tetraethyl 
orthosilicate by a sol-gel method. In this polymerization product, either 
ends of the diorganopolysiloxane can be bonded to the branch center, and 
the structure is not clear. There have not been any reports of so-called 
star-type organopolysiloxanes having polysiloxane a SiO.sub.2 unit as the 
branch center bonded to one end of diorganopolysiloxane components. We 
have proposed novel branched polysiloxanes and a method for their 
manufacture (Japanese Patent Application Nos. Hei 3{1991}-286745, Hei 
3{1991}-286753). 
As described above, the present invention provides a novel method for the 
manufacture of branched polysiloxanes with clear structure. These 
compounds are useful as starting materials for silicone elastomers or 
reinforcing agents. They are also useful as additives for improving flow 
characteristics of silicone fluids. 
SUMMARY OF INVENTION 
The present invention is a novel method for the manufacture of branched 
polysiloxanes having the polysiloxane SiO.sub.4/2 unit as the branch 
center precisely bonded to one end of a diorganopolysiloxane. The present 
invention concerns a method for the manufacture of a branched polysiloxane 
characterized by reacting a linear polysiloxane with a reactive 
polysiloxane having halogen substitution.

DESCRIPTION OF INVENTION 
The present invention is a novel method for the manufacture of branched 
polysiloxanes having the plysiloxane unit SiO.sub.4/2 as the branch center 
precisely bonded to one end of a diorganopolysiloxane. The present 
invention comprises a method for the manufacture of a branched 
polysiloxane described by formula (III), the method characterized by 
reacting a linear polysiloxane described by formula (I) with a reactive 
polysiloxane described by formula (II). 
The linear polysiloxanes useful in the present process are described by 
formula 
EQU R.sup.1 (R.sup.2 R.sup.3 SiO).sub.a M, (I) 
where each R.sup.1, R.sup.2, and R.sup.3 is independently selected from a 
group consisting of hydrogen atom, alkyls comprising one to eight carbon 
atoms, haloalkyls comprising one to eight carbon atoms, alkenyls 
comprising two to eight carbon atoms, and aryls; 1.ltoreq.a.ltoreq.1000; 
and M is selected from a group consisting of hydrogen atom and alkali 
metal atoms. 
The reactive polysiloxanes useful in the present process are described by 
formula 
EQU (SiO.sub.42).sub.x (R.sup.4.sub.2 QSiO.sub.12).sub.y (R.sup.5.sub.2 R.sup.6 
SiO.sub.1/2).sub.W, (II) 
where R is selected from a group consisting of hydrogen atom and alkyls 
comprising one to eight carbon atoms; each R.sup.4 and R.sup.5 is 
independently selected from a group consisting of alkyls comprising one to 
eight carbon atoms, haloalkyls comprising one to eight carbon atoms, 
alkenyls comprising two to eight carbon atoms, and aryls; R.sup.6 is 
selected from a group consisting of hydrogen atom, alkyls comprising one 
to eight carbon atoms, haloalkyls comprising one to eight carbon atoms, 
alkenyls comprising two to eight carbon atoms, and aryls; Q is a halogen 
atom; 2.ltoreq.x.ltoreq.500, 2.ltoreq.y+z+w.ltoreq.150; 2.ltoreq.y; 
O.ltoreq.z; O.ltoreq.w.ltoreq.15; 0.3.ltoreq.(y+z+w)/x.ltoreq.3; 
O.ltoreq.w/(y+z+w).ltoreq.0.1). 
Branched polysiloxanes which can be prepared by the present method are 
described by formula 
EQU (SiO.sub.4/2).sub.x (R.sup.4.sub.2 ASiO.sub.1/2).sub.y (R.sup.5.sub.2 
R.sup.6.sub.SiO.sub.1/2).sub.z (RO.sub.1/2).sub.w, (III) 
where A is described by the formula (OSiR.sup.2 R.sup.3).sub.a R.sup.1, 
R.sup.1,R.sup.2, and R.sup.3 are as previously described; 
1.ltoreq.a.ltoreq.1000; and all other values and substituents are as 
previously described. 
In the linear polysiloxanes, formula (I), used in the present invention, 
the substituents R.sup.1, R.sup.2, and R.sup.3 alkyl groups such as methyl 
group, ethyl group, propyl group, butyl group; haloalkyl groups such as 
3,3,3- trifluoropropyl group, etc; alkenyl groups such as vinyl groups, 
allyl group, butenyl group, etc.; aryl groups such as phenyl group, etc. 
R.sup.1, R.sup.2, and R.sup.3 may be the same or different. 
The degree of polymerization of the linear polysiloxanes a is 1-1000. The a 
value determines the length of the branches in the branched polysiloxanes. 
When the value a exceeds 1000, the overall molecular weight of the 
polysiloxane becomes too big, with very high viscosity. A practical 
preferred range of a is 1-800, more preferably 1-500. 
The ends of the linear polysiloxane molecules are silanol or silanol metal 
salts. In the case of silanol metal salts, the alkali metal atom M may be 
lithium, sodium, potassium, cesium, etc., while lithium is preferred. 
While there are no restrictions on the methods for the manufacture of the 
linear polysiloxanes used in the present invention, the following method 
is recommended for polysiloxanes of uniform degree of polymerization, 
namely, a ring-opening polymerization of cyclic polysiloxanes in the 
presence of alkali metal compounds. While any cyclic polysiloxanes having 
the substituents R.sup.2 and R.sup.3 can be used, more preferred in terms 
of reactivity are cyclotrisiloxane, cyclotetrasiloxane, 
cyclopentasiloxane, cyclohexasiloxane, etc. These compounds may be use 
singly or as mixtures thereof. Such cyclic polysiloxanes are reacted with 
alkali metal compounds in the presence or absence of organic solvents for 
the ring-opening polymerization to botain linear polysiloxanes. 
While not restricted in any particular way, organic solvents with a certain 
polarity are preferred for good solubility of the cyclic polysiloxanes, 
product linear polysiloxanes and also final-product branched 
polysiloxanes. In some case, good results are obtained when mixtures of 
polar and nonpolar solvents are used. Suitable solvents are aliphatic 
hydrocarbons such as hexane, heptane, octane, etc.; aromatic hydrocarbons 
such as benzene, toluene, xylene, etc; ether compounds such as diethyl 
ether, dibutyl ether, diphenyl ether, tetrahydrofuran, 1,4-dioxane, etc.; 
chlorine compounds such as carbon tetrachloride, chloroform, 
trichloroethane, etc. However, suitable solvents are not limited to the 
examples given above. 
The alkali metal compounds that can be used are alkyl, aryl, and amide 
compounds of alkali metal such as lithium, sodium, potassium, cesium, etc. 
Preferred are readily available alkali metal methyl, ethyl, propyl, butyl, 
phenyl compounds, etc., while butyllithium is especially preferred. 
The reactive polysiloxanes, formula (II), can be prepared, e.g., by 
reacting hydrogen-functional polysiloxanes described by formula 
EQU (SiO.sub.4/2).sub.X (R.sup.4.sub.2 HSiO.sub.1/2).sub.y (R.sup.5.sub.2 
R.sup.6 SiO.sub.1/2).sub.Z (RO.sub.1/2).sub.W, (IV) 
where R, R.sup.4, R.sup.5, R.sup.6, x, y, z, and w are as defined for the 
branched polysiloxane, formula (III), with halogen compounds such as 
carbon tetrachloride under energy-beam irradiation or in the presence of 
metal chlorides or radical initiators. 
Such reactive polysiloxanes are than reacted with linear polysiloxanes at 
room temperature, under cooling, or under heating, usually at -80.degree. 
C. to 200.degree. C., while a more proper temperature range is from 
-25.degree. C. tp 160.degree. C. 
In the case of linear polysiloxanes with silanol terminal groups, this 
reaction is performed preferably in the presence of a hydrogen halide 
trapping agent. While not restricted in any particular way, the hydrogen 
halide trapping agents that can be used are organic bases such as 
triethylamine, pyridine, etc., and inorganic bases such as ammonia, etc. 
The branched polysiloxanes thus obtained contain x SiO.sub.4/2 units in a 
molecule, and this part becomes the siloxane center, namely the nucleus. 
The value of x is above one, especially above 4, without any restrictions 
in the upper limit. However, in general, when x exceeds 500, the resulting 
branched polysiloxanes have very poor solubility in organic solvents, thus 
handling becomes very difficult. Considering workability, x should be 
below 300, more preferably below 150. 
The number of the (.sup.4.sub.2 ASiO.sub.1/2) units, an important part of 
the branched polysiloxanes of the present invention, is y in a molecule. 
There are not any special restrictions on y, as long as it is 2 or more, 
while a value of 3 or more for y is preferred in terms of branching. The 
upper limit of y is 150. Making polymers of higher y values is difficult. 
The (R.sup.5.sub.2 R.sup.6 SiO.sub.1/2) unit is not essential in the 
branched polysiloxanes of the present invention, thus the z value may be 
zero. This unit controls the number of branches and size of nucleus in the 
branched polysiloxanes of the present invention. Namely, the (y+z+w)/x 
value determines the size of the nucleus; the nucleus size increases with 
decreasing (y+z+w)/x value. At the same nucleus size, the number of 
branches increases with decreasing z value. There is an upper limit on the 
z value, since synthesizing molecules with a (y+z+w)/x value. At the same 
nucleus size, the number of branches increases with decreasing z value. 
There is an upper limit on the z value, since synthesizing molecules with 
a (y+z+w) value above 150 is very difficult. 
Depending on the conditions for the synthesis of the hydrogren-functional 
polysiloxanes, formula (IV), for the starting materials used in the 
polysiloxane reaction preparation, there may be residual (RO.sub.1/2) 
units, which should be less than 15 in a molecule. The content of these 
based on the sum of all the units except (SiO.sub.4/2) should be less than 
10 mol%. 
The monofunctional unit to tetrafunctional unit ratio (y+z+w)/x is from 0.3 
to 3. With decreasing (y+z+w)/x value, the polysiloxane molecular weight 
increases; however, it is not favorable for this value to be below 0.3, 
because a marked decrease in the polysiloxane solubility in organic 
solvents occurs. On the other hand, if this value exceeds 3, it is also 
not favorable because the molecular weight is too small. The most suitable 
range is 0.3 to 2. 
Each of the substituents R.sup.4 and R.sup.5 may be independently selected 
from a group consisting of alkyls comprising one to eight carbon atoms, 
haloalkyls comprising one to eight carbon atoms, alkenyls comprising two 
to eight carbon atoms, and aryls. For terms of ecomony it is preferred 
that each R.sup.4 and R.sup.5 be independently selected from a group 
consisting of methyl, vinyl, and phenyl. 
The substituent A corresponds to diorganopolysiloxanes described by formula 
(OSiR.sup.2 R.sup.3).sub.aR.sup.1, namely, the linear polysiloxane minus 
the alkali metal or hydrogen atom M. 
The present invention is further explained with the following examples. 
However, the present invention is not limited to such examples. 
EXAMPLE 1 
(Not within the scope of the present invention.) 
Preparation of reactive polysiloxane of formula (SiO.sub.4/2).sub.22 
(Me.sub.2 ClSiO.sub.1/2).sub.20 in 100 mL of carbon tetrachloride was 
treated with 3.0 g of benzoyl peroxide. The resulting mixture was then 
heated under reflux for 40 h and freed from the solvent by distillation. 
The residue was treated with n- hexane, filtered from the insolubles and 
freed from the n- hexane by distillation to obtain 25 g (yield 99%) of a 
polymer corresponding to (SiO.sub.4/2).sub.22 (Me.sub.2 C1SiO.sub.1/2) 
Example 2 
(Not within the scope of the present invention.) 
Preparation of reactive polysiloxane of formula (SiO.sub.4/2).sub.22 
(Me.sub.2 ClSiO.sub.1/2).sub.16 (Me.sub.3 SiO.sub.1/2).sub.4. A solution 
of 20 g of hydrogen-functional polysiloxane represented by 
(SiO.sub.4/2).sub.22 (Me.sub.2 ClSiO.sub.1/2).sub.16 (Me.sub.3 
SiO.sub.1/2).sub.4. A solution of 20 g of hydrogen-functional polysiloxane 
represented by (SiO.sub.4/2).sub.22 (Me.sub.2 HSiO.sub.1/2).sub.16 
(Me.sub.3 SiO.sub.1/2).sub.4 in 100 mL of carbon tetrachloride was treated 
with 2.3 g of palladium chloride; the resulting mixture was then heated 
under reflux for 40 h and filtered from the palladium chloride to botain 
23.8 (yield 99%) of a polymer corresponding to (SiO.sub.4/2).sub.22 
(Me.sub.2 ClSiO.sub.1/2) Me.sub.3 SiO.sub.1/2).sub.4. 
Example 3 
A solution of 8.6 g of 1,3,5,7-tetramethyl- 
1,3,5,7-tetravinylcyclotetrasiloxane in 150 mL of tetrahydrofuran in an 
ice bath at 0.degree. C. was treated with 59 mL of 1.69 mol n-butyllithium 
solution in hexane over a period of 30 min; this was then treated with a 
hexamethylcyclotrisiloxane solution in tetrahydrofuran (corresponding to 
133 g hexamethylcyclotrisiloxane), and stirred continuously, while the 
hexamethylcyclotrisiloxane consumption was traced by gas chromatography 
until the conversion reached above 95%. The reaction mixture was then 
treated with 16.7 g of the reactive polysiloxane from Example 1 and 
stirred further for 1 h. The solid formed was filtered out, washed with 
water and dried to obtain 136 g (yield 85%) of a polymer corresponding to 
(SiO.sub.4/2).sub.22 (Me.sub.2 AsiO.sub.1/2).sub.20 (where A represents 
(OSiME.sub.2).sub.180 SiMenVuVi; Me=methyl, nBu=n-butyl, Vi=vinyl). Gel 
permeation chromatography revealed a number- average molecular weight of 
20,700 and dispersivity of 1.6. Other analysis revealed: IR: 1091, 1024 
cm.sup.-1 (Si-O-Si); .sup.1 H- NMR (CDC1.sub.3 solvent, CHC1.sub.3 
standard, .beta.=7.24 ppm): 0-0.1 (s, 105H), 0.6 (t, 2H), 0.9 (t, 3H), 1.3 
(m, 4H), 5.7-5.8 (q, 1H), 5.9-6.0 (q, 1H), 6.0-6.1 (q, 1H); .sup.29 Si-NMR 
(CDC1.sub.3 solvent, TMS standard, .delta.=0 ppm); -4.0 (SiViMenBu), -21 
to -22.5 (SiMe.sub.2), and -110.9 (SiO.sub.4/2). 
Example 4 
Example 3 was repeated using 20.3 g of the reactive polysiloxane prepared 
in Example 2 to obtain 143 g (yield 87%) of a polymer corresponding to 
(SiO.sub.4/2).sub.22 (Me.sub.2 ASiO.sub.1/2).sub.16 (Me.sub.3 SiO.sub.1/2) 
(where A=(OSiMe.sub.2).sub.180 SiMenBuVi) with an average molecular weight 
of 14,500. 
Example 5 
Example 3 was repeated using 187 g of 
1,3,5-trimethyl-1,3,5-tris(3,3,3-trifluoropropyl)cyclotrisiloxane in place 
of the hexamethylcyclotrisiloxane solution in tetrahydrofuran to obtain 
(SiO.sub.4/2 .sub.22 (Me.sub.2 ASIO.sub.1/2).sub.20 (where A=(OSiMeC.sub.2 
H.sub.4 CF.sub.3).sub.120 SiMenBuVi) at a yield of 88% with an average 
molecular weight of 12,500. Analysis showed: IR:1071, 1020 cm.sup.-1 
(Si-O-Si); .sup.1 H-NMR (CD.sub.3 COCD.sub.3 solvent, CH.sub.3 COCH.sub.3 
standard, .beta.=2.04 ppm): 0.1-0.3 (m, 45H), 0.6 (t, 2H), 0.8-0.9 (m, 
27H), 1.3 (m, 4H), 2.1-2.3 (m, 24H), 5.7-5.8 (q, 1H), 5.9-6.0 (g, 1H), and 
0.6-6.1 (q, 1H); .sup.29 Si-NMR (CD.sub.3 COCD.sub.3 solvent, TMS 
standard, .beta.=0 ppm): -2.2 (SiViMenBu), -20.0 (SiMe.sub.2), -22.1 
(SiC.sub.2 H.sub.4 CF.sub.3), and -110.9 (SiO.sub.4/2). 
Example 6 
Example 3 was repeated using a hexaphenylcyclotrisiloxane solution in 
diphenyl ether, that is 119 a hexaphenylcyclotrisiloxane in place of the 
hexamethylcyclotrisiloxane solution in tetrahydrofuran. The method was 
conducted at a reaction temperature of 160.degree. C. and a reaction time 
of 15 h to botain (SiO.sub.4/2).sub.22 (Me.sub.2 ASiO.sub.1/2).sub.20 
(where A=(OSiPh.sub.2).sub.60 SiMenBuVi and Ph=phenyl) at a yield of 58% 
with an average molecular weight of 15,000.