PROCESS FOR PREPARING SULFUR CONTAINING POLYSILOXANE POLYMERS, THE PRODUCTS OBTAINED THEREBY AND THE USE OF THE PRODUCTS AS CROSS-LINKING AGENTS

Abstract: The invention relates to a process for preparing sulfur containing polysiloxane polymers having only units of the general formula (M) x (T′) y wherein M represents an R₃SiO 0.5 unit in which R is a mono­ valent hydrocarbon radical or a halogenated monovalent hydrocarbon radical having from 1 to 18 carbon atoms, T′ represents a unit of the formula (R″S) z R′ SiO 1.5 in which R′ is a divalent, trivalent or tetravalent hydrocarbon radical having from 2 to 18 carbon atoms or divalent, trivalent or tetravalent hydrocarbon radicals having at least one -C-S-C-group, R″ is hydrogen or R, x and y each represent a number greater than 1 and up to 20,000 in which the ratio of x to y may vary from 1:0.33 to 0.005:1 and z is 1, 2 or 3. These sulfur containing polysiloxane polymers are pre­ pared by reacting in the presence of an acid catalyst a mixture containing (1) a hexaorganodisiloxane and (2) a silicon com­ pound having the formula (R″S) z R′ Si (OR)₃ in which R, R′ and R″ are the same as above. The products obtained thereby, which are free of R₂SiO units, are useful as cross-linking agents in free radical polymerizations.

Description: Process for preparing sulfur contain ing polysilöxone polymersm the pro ducts obtained thereby and the use of the products as cross-linking agents. The present invention relates to a process for preparing polysiloxane polymers and more particularly sulfur containing polysiloxane polymers and to the products obtained thereby. Polysiloxane polymers, especially polwsiloxane polymers containing sulfur atoms are described in U.S. Patent 4,046,795, in which a disiloxane and/or a hydrocarbonoxy or hydroxy containing silane or siloxane is reacted with a cyclic trisiloxane in the presence of an acid catalyst, in which at least one of the above organosilicon compounds contain an R' (SR"')y group, in which R' is a divalent, trivalent or tetravalent hydrocarbon radical, R"' is hydrogen or a monovalent hydrocarbon radical and y is a number of from 1 to 3. The resultant polysiloxane polymers contain MDT' structural units in which M represents an RDSiOo 5 unit, D represents an R2SiO unit and T' represents a unit of the formula (R"'S)R'SiO1 in which R' and R"' are the same as above and R is a monovalent hydrocarbon radical or a halogenated monovalent hydrocarbon radical Compared to the polysiloxane polymers described in the above patent, the polysiloxane polymers of the present invention contain (M)x(T')y structural units instead of the MDT' units. Polysiloxane polymers which are free of the "D" units have certain advantages over polysiloxanes containing "D" units. Sor example, the polysiloxanes of this invention which are free of the "D" units are more compatible with organic compounds while retaining some of the silicon compound characteristics. Moreover, the polysiloxane polymers of this invention may be reacted with cyclic siloxanes such as octaorganocyclotetrasiloxanes to form polysiloxane polymers containing "D" units. Also, U.S. Patent 3,794,672 describes perfluoroalkyl silicon compounds containing sulfur which are prepared by reacting olefins of the formula RfCR=CH2 with a silicon compound of the formula HSR Si Zm 03-n-' 2 in tbe presence of free radical generators, such as peroxides, in which Rf is a perfluoroalkyl radical, R is an alkylene radical, X is chlorine, acetoxy or an alkoxy radical, n is O to 2, and m is O to 3 and the sum of n + m is not greater than 3. In contrast to the teachings of U.S. Patent 3,794,672, it has been found that polysiloxane polymers having (M)x(T')y struc- tural units can be prepared by reacting a disiloxane with a mercapto- or tbiofunctional trihydrocarbonoxysilane. Therefore, it is an object of the present invention to provide polysiloxane polymers which are more compatible with organic compounds while retaining some of the characteristics of the silicon compounds. Another object of this invention is to provide polysiloxane polymers which are free of the "D"(R2SiO) units. Still another-object of this invention is to provide polysiloxane polymers which may be used as crosslinking agents in free-radical polymerizations. A further object of this invention is to provide a method for preparing polysiloxane polymers which are free of "D" (R2SiO) units. The foregoing objects and others which will become apparent from the following description are accomplished in accordance with this invention, generally speaking, by providing polysiloxane polymers having only the structural units (M)x(T')y in which M represents an R3SiO0.5 unit and T' represents a unit of the formula (R" S)zR'SiO1.5 in which R is a monovalent hydrocarbon radical or a halogenated monovalent hydrocarbon radical having from 7 to 18 carbon atoms and R' represents a divalent, trivalent or tetravalent hydrocarbon radical having from 2 to 18 carbon atoms or divalent, trivalent or tetravalent. hydrocarbon radicals having at least one -C-S-C- group and R" is hydrogen or R, x and y are numbers each greater than 1 and up to 20,000, in which the ratio of x to y may vary from 1:0.33 to 0.005:1 and z is 1, 2 or 3. The polysiloxane polymers which have units of the formula [(R"S) Rs Si015)y (00 5SiR3) are prepared by reacting (1) a disiloxane with (2) a silicon compound of the formula (R"S)z R' Si(OR)3 in which R, R', R", x, y and z are the same as above, in the presence of an acid catalyst. Examples of hydrocarbon radicals represented by R above are alkyl radicals, such as methyl, ethyl, propyl, butyl, octyl, decyl, dodecyl and octadecyl radicals; aryl radicals, such as phenyl and naphthyl radicals; cycloalkyl radicals, such as cyclopentyl, cyclohexyl and cycloheptyl radicals; aralkyl radicals, such as benzyl, phenylethyl, phenylpropyl and phenylbutyl radicals; alkaryl radicals, such as tolyl, xylyl and ethylphenyl radicals; halogenated hydrocarbon radicals, such as haloalkyl and haloaryl radicals, e.g., chloromethyl, chloroethyl, chlorobutyl, chlorophenyl, tetrachlorophenyl and difluorophenyl radicals. Examples of divalent radicals represented by R' are alkylene radicals, such as ethylene, trimethylene, hexamethylene, octamethylene, dodecylmethylene; arylene radicals, such as phenylene, biphenylene radicals and the corresponding alkylene and arylene radicals containing at least one C-S-C unit. Suitable examples of trivalent and tetravalent hydrocarbon radicals represented by R' are those of the formula CHCH2-, =CHCH2CH2-, =CH(CH2)3-, =CH(CH2)4-, =CH(CH2)17-, EMI4.1 and the like. Suitable examples of the group (R11S) zR' are -CH2SH, -C2H4SH, -C3H6SH, -CH2SC4H9, -C2H4SC2H5, -C3H6SC6H5, (HSCH2)2CHCH2CH2-, (HSCH2CH2)(HSCH2)CH(CH2)4-, (HSCH2CH2)(HSCH2)CH(CH2)-, (HSCH2CH2)(HSCH2)CHCH(CH2SH)CH2-, CH2CH2-, HS(CH2)5CH(CH2CH2SH)CH2CH2CH(CH2CH3)-, (HSCH2CH2)2CHCH2CH2-, (HSCH2)2CHSCH2CH2-, (HSCH2)2(C2H5)CCH2SCH2CH2CH2-, (HSCH2)3CCH2SCH2CH2CH2-, (HSCH2)(HSCH2CH2CH2CH2)CHSCH2CH2CH2-, (HSCH2CH2)2CHCH2SCH2CH2CH2-, (HSCH2)2(C2H5)CCH2SCH2CH2S(CH2)3-, (HSCH2)3CCH2S(CH2)3S(CH2)3-, EMI5.1 Examples of suitable sulfur containing silicon compounds (2) are silanes such as 3-mercaptopropyltrimethoxysilane, 2-mercap- toethyltriethoxylane, #-mercaptodecyltriethoxysilane, #-mercaptohexy ltripropoxylane, #-mercaptoamyltriethoxy silane, 2-(triethoxysilyl)ethyl butyl thioether, 3-(trimeth- oxysilyl)propyl butyl thrioether, 4-(triethoxysilyl)butyl methyl thioether, 2-(tripropoxysilyl)ethyl methyl thioether, 2-(tributoxysilyl) ethyl phenyl thioether, 2- (triethoxysilyl) ethyldodecyl thioether, 6-(trimethoxysilyl)hexyl ethyl thioether. Suitable examples of disilioxanes (1) which may be employed in this invention are hexamethyldisiloxane, hexaethyldisilox ane, hexapropyldisiloxane, hexaheptyldisiloxane and hexaoctyldisiloxane, with the preferred disiloxane being hexamethyldisiloxane. The polysiloxane polymers of this invention are prepared by affecting a reaction between a disiloxane (1) and a sulfur containing silicon compound (2) in the presence of an acid catalyst. Catalysts which may be employed in affecting the reaction are acid clays and organic and inorganic acids having a pEa value less than 1.0 and more preferably below 0.7 in aqueous solutions. Suitable acid catalysts which may be employed are benzosulfonic acid, p-toluenesulfonic acid, sulfuric acid, sulfurous acid, nitric acid, perchloric acid, hydrochloric acid and acid-activated clays such as known under the registered trademarks "Filtrol No. 13 and No. 24" (available from Filtrol Corporation). Although the amount of catalyst is not critical, it is preferred that from about 0.003 percent up to about 10 percent by weight of catalyst based on the total weight of the reactants, i.e., the sulfur containing silicon compound (2) and disiloxane (1), be employed in the reaction to make the polysiloxane polymers of this invention. Greater amounts of catalyst may be used, however, it is the intent of this invention to provide a catalyst system which does not alter the functionality of the resultant composition. Generally, it is desirable to remove or destroy the catalysts after the reaction is complete because¯their presence will adversely affect the properties of the resulting polymer. The catalysts may be removed, for example, by washing with water or they may be destroyed by neutralizing with basic reagants. In addition, certain catalysts, for example, acidactivated clays, may be removed by filtering the reaction mixture. The ratio of disiloxane (1) to sulfur containing silicon compound (2) is not critical and may range from 0.01 to 6.7 molts of disiloxane (1) per mol of sulfur containing silicon com pound (2) and more preferably from 0.5 to 1.5 mols of disiloxane (1) per mol of sulfur containing silicon compound (2). The reactions may be conducted at any temperature ranging from about 250 up to about 2000C over a period of time ranging from 0.5 hour up to several days. The reaction may be conducted in the absence of a solvent; however, when a solvent is employed, it may be employed in an amount of from about 1 to 50 percent by weight based on the disiloxane (1) and sulfur containing silicon compound (2). Examples of suitable hydrocarbon solvents are heptane, benzene, toluene, xylene and the like. Moreover, it is preferred that the reaction be conductedain an inert atmosphere. The polysiloxane polymers of this invention which are free of "D" (R2SiO) units are useful as cross-linking agents in free radical polymerizations such as those which utilize ultra violet light and a photo initiator. These polymers are also more compatible with organic compounds than polysiloxanes used heretofore, while retaining some of the advantages of the silicon compounds. Moreover, these polymers may be used as intermediates in the formation of polysiloxanes containing B" (R2SiO) units by reacting the polysiloxane polymers of this invention with the more readily available cyclic siloxanes, such as octaorganocyclotetrasiloxanes. Various embodiments of this invention are illustrated in the following examples in which all parts are by weight unless otherwise specified. Example 1 To a one liter reaction vessel is added 243 parts of hexa methyldisiloxane, 196 parts of 3-mercaptopropyltrimethoxysilane, 196 parts of water, 100 parts of heptane and 5 parts of an acid-activated clay ("Filtrol No. 13" acid clay, available from Filtrol Corporation). The vessel is heated to 800C and maintained at this temperature for three hours. The contents of the vessel are then cooled to room temperature and filtered. The volatiles are removed by heating for 2 hours at 1500C at less than 133 Pa (1 torr). A clear, transparent liauid is obtained having a viscosity of 871 mm2/s (cs.) at 25 C. Nuclear Magnetic Resonance (NMR) analysis shows that the product has a mol ratio of ZSC3H6:Si(CH3)3 of 1.0:0.81. The SH content of the product is about 14.4 percent. Example 2 The procedure of Example 1 is repeated except that 121.5 parts of hexamethyldisiloxane and 10 parts of an acid-activated clay ("Filtrol No. 13" acid clay) are used. A turbid fluid is obtained having a viscosity of ?4O mm2/s (cs.) at 250C and an SH content of 19.7 percent. Nuclear Magnetic Resonance (NMR) analysis shows that the product has a mol ratio of HSC3H6: Si(CE3)3 of 1.0:0.92. Example 3 The procedure of Example 1 is repeated, except that 15 parts of hydrochloric acid (37 %) is substituted for the acid-activated clay (',Filtrol No. 13" acid clay). The reaction mixture is neutralized with 50 parts of sodium bicarbonate, filtered and the volatiles removed by heating unter reduced pressure for 2 hours at 1500C. A turbid liquid is recovered and analyzed by Nuclear Magnetic Resonance (NMR). The resultant product has a viscosity of 432.8 mm2/s (cs.) at 25 C, an SR content of 20.9 percent and a mol ratio of HSC3H6:Si(CH)3 of 1.0:0.81. Example 4 The procedure of Example 3 is repeated, except that 5 parts of sulfuric acid (96 %) is substituted for the hydrochloric acid. The resultant product has a viscosity of 1,361 mm2/s (cs.) at 250C, an SH content of 16.6 percent and a mol ratio of HSC3H6:Si(CH3)3 of 1.0:1.33.

Claims: C l a i m s : 1. A process for preparing sulfur containing polysiloxane polymers containing the structural units of the general formula (M)X(T')y wherein M represents a unit of the formula R3SiOo 5 and 2' represents a unit of the formula (R"S) zR' SiO1 5 which comprises reacting (1) a hexaorgano disiloxane with.(2) a silicon compound of the formula (R"S)z R' Si (OR)3 in the presence of an acid catalyst, in which R is selec ted from the group consisting of monovalent hydrocarbon radicals and halogenated monovalent hydrocarbon radicals having from 1 to 18 carbon atoms, R' is selected from the group consisting of divalent, trivalent and tetravalent hydrocarbon radicals having from 2 to 18 carbon atoms and divalent, trivalent and tetravalent hydrocarbon radicals having at least one C-S-C-group, R" is selected from the group consisting of hydrogen, and R, x and y are each greater than 1 and up to 20,000, where the ratio of x to y may vary from 1:0.33 to 0.005: 1 , and z is 1, 2 or 3. 2. The process of claim 1, wherein the hexaorganodisiloxane is a hexaalkyldisiloxane. 3. The process of claim 2, wherein the hexaalkyldisiloxane is hexamethyldisiloxane. 4. The process of claim 1, wherein R is an alkyl radical and R' is a divalent radical. 5. The process of claim 1, wherein R" is hydrogen. 6. The process of claim 1, wherein R'l is a monovalent hydro carbon radical. 7. The process of claims 5 or 6, wherein z is 1. 8. The products prepared in accordance with the process of claim 1. 9. Use ot the products prepared in accordance with the process of claim 1 as cross-linking agents in free radical poly merizations. Claims : (For Austria) 1. A process for preparing sulfur containing polysiloxane polymers containing the structural units of the general formula (M)x(T')y wherein M represents a unit of the formula R3SiOo 5 and T' represents a unit of the formula (R"S) zR' SiO1 5 which comprises reacting (1) a hexaorgano disiloxane with.(2) a silicon compound of the formula (R"S)z R' Si (OR)3 in the presence of an acid catalyst, in which R is selec ted from the group consisting of monovalent hydrocarbon radicals and halogenated monovalent hydrocarbon radicals having from 1 to 18 carbon atoms, R' is selected from the group consisting of divalent, trivalent and tetravalent hydrocarbon radicals having from 2 to 18 carbon atoms and divalent, trivalent and tetravalent hydrocarbon radicals having at least one -C-S-C-group, R" is selected from the group consisting of hydrogen, and R, x and y are each greater than 1 and up to 20,000, where the ratio of x to y may vary from 1:0.33 to 0.005: 1 , and z is 1, 2 or 3. 2. The process of claim 1, wherein the hexaorganodisiloxane is a hexaalkyldisiloxane. 3. he process of claim 2, wherein the hexaalkyldisiloxane is hexamethyldisiloxane. 4. The process of claim 1, wherein R is an alkyl radical and R' is a divalent radical. 5. The process of claim 1, wherein R" is hydrogen. 6. The process of claim 1, wherein R" is a monovalent hydro carbon radical. 7. The process of claims 5 or 6, wherein z is 1. 8. Use of the products prepared in accordance with the process of claim 1 as cross-linking agents in free radical poly merizations.

Inventors: MARTIN, EUGENE RAY
Applicants: SWS SILICONES CORPORATION
Application year: 1981
Main classification: C08G77
IPC codes: C08G77