WO2002018393A2

WO2002018393A2 - Process for making oligomeric polyalkoxysiloxanes, novel tetramethoxysilane oligomer, and uses therefor

Info

Publication number: WO2002018393A2
Application number: PCT/US2001/025441
Authority: WO
Inventors: Sigfredo Gonzalez; Robert Adam Kayser; James Stephen Ritscher; Tiberiu L. Simandan
Original assignee: Crompton Corp
Current assignee: Lanxess Solutions US Inc
Priority date: 2000-08-25
Filing date: 2001-08-14
Publication date: 2002-03-07
Anticipated expiration: 2003-02-25

Abstract

Tetramethoxysilane is reacted with water and/or carboxylic acids in a certain ratio and in the presence of a strong acid catalyst to produce silanol-free oligomers. A wide variety of equilibrium products may be prepared from the oligomers.

Description

PROCESS FOR MAKING OLIGOMERIC POLYALKOXYSILOXANES, NOVEL TETRAMETHOXYSLLANE OLIGOMER, AND USES THEREFOR

BACKGROUND OF THE INVENTION

FIELD OF THE INVENTION

The present invention provides a novel tetramethoxysilane oligomer, a synthesis method therefor, and novel uses of tetraalkoxysiloxane oligomers.

DESCRIPTION OF THE PRIOR ART

Hydrolysis products of tetraalkoxysilanes, also known as orthosilicates, have been known for a long time. Glasses, aerogels and xerogels, and various silica products are routinely produced from sol-gels prepared from hydrolyzed tetraalkoxysilanes. The procedures usually involve the use of aqueous alcoholic solutions and carefully controlled pH to perform the hydrolysis all the way to silica gel. Tetramethoxysilane (TMOS) is a by-product from the trimethoxysilane (TMS) direct synthesis process. Due to the fact that this TMOS is not a result of a chlorosilane alcoholysis (silicon tetrachloride), it is naturally free of residual chlorides. It is a very good starting material for oligomeric polyalkoxysiloxanes used as starting reagent for crosslinking agents for thermoplastic polyolefins, for anti-corrosive coatings for metals, for reconstructive or restorative building materials for use on brick, concrete, limestone and mortar, and for highly active surfactants for urethane foams, as well as a precursor for fumed silica and fused quartz. TMOS as well as tetraethoxysilane (TEOS) and oligomeric polyalkoxysiloxanes can also be used to produce high quality silicas for catalysts, fillers, electronic components, optical fibers, etc.

TMOS has a high toxicity. Consequently it is not conveniently shipped from the site of production, especially in large quantity. This significantly limits the uses to which TMOS may be put, and the manner in which it may be used. Langkammerer, US 2490691, describes the polymerization of C₂ and higher tetraalkoxysilanes to form alkylpolysilicates. The process described therein comprises heating the tetraalkylsilicates with anhydrous carboxylic acids at a silicate/acid ratio of 1 :0.5-2. This process provides high molecular weight polymeric esters of polysilicic acid which are liquid and soluble in organic solvents. engrovius, US 4950779, describes non-aqueous polymerizations of polyalkoxysilanes, such as methyltriethoxysilane or vinyltriethoxysilane to produce oligomers and polymers using mild temperatures and equal molar amounts of formic acid and silane. An ion exchange resin is optionally used as a catalyst.

Horn, et al., US 5282998 describes a process for the synthesis of vinyl alkoxysilane copolymer oligomers using controlled amounts of water. The reaction is catalyzed by hydrochloric acid. The patent examples show that a minor amount of tetraethoxysilane may be incorporated into the copolymer oligomers.

In US 5576408 from the same company, a similar process is claimed to produce water-based organic polysiloxane-containing compositions.

US 5679147 describes preparation of low molecular weight organosiloxanes terminated with silanol groups, using a cation exchange resin as catalyst.

US 5441718 teaches that oligomers formed with silanes containing non- hydrolyzable organic substituents have a limited ability to form gels. With tetraalkoxy silanes, however, crosslinked gels are readily formed using a strong carboxylic acid such as formic acid at an acid/silane mole ratio of at least 1.5:1, together with at least a small amount of water.

Klemperer, et al.., "Molecular growth pathways in silica sol-gel polymerization", Polym. Prepr. (Am. Chem. Soc, Div. Polym. Chem.J, (1987), 28(1), 432-3, reports an analytical procedure for determining the composition and structures of low-molecular- weight polysilicates formed in hydrolysis and condensation of Si(OMe)₄ to study the molecular growth pathway in silica sol-gel polymerization. The procedure involved reaction quenching and derivatization of silanol groups with diazomethane (CH^N^, fractional distillation, and analysis of the fraction using gas chromatography-mass spectroscopy and NMR.

Sailor, et al., Science (1997) 276, 1826-1828, reports obtaining white phosphors from silicate-carboxylate sol-gel precursors. The gel-yielding reaction of TMOS and TEOS with a variety of organic carboxylic acids (formic, lactic, acetic, trifluoroacetic, cyclopropanoic, malonic, citric, tartarϊc, glyoxylic, and oxalic) at room temperature at times ranging from a few minutes to a few days was studied. The reaction products were total hydrolyzates which, after thermal treatment (in air) between 200° and 500°C, produced a white or yellowish solid material that underwent photoluminescence.

SUMMARY OF THE INVENTION

The present invention presents a method to produce low-molecular- weight oligomer of tetramethoxysilanes, novel oligomers of tetramethoxysilane, and various applications in which oligomers of tetramethoxysilanes may be usefully employed.

The method starts with tetramethoxysilane, water and/or carboxylic acids in a certain ratio in connection with the final viscosity and average molecular weight of the product, in the presence of lipophilic homogeneous acidic catalysts or heterogeneous cation exchange resins. Water and/or carboxylic acids are employed as hydrolyzing agents and are taken together for purposes of calculating reactant mole ratios. Surprisingly, silanol-free oligomers are readily obtained even when water is used. A strong acid catalyst is used. Lipophilic acid catalysts, particularly alkyl sulfonic acids or heterogenized catalysts from the class of strongly acidic ion exchange resins, may be used. In cases in which an acidic product is not acceptable, the acidic ionic exchange resins are preferred because of their advantages related to easy removal from the products at the end of the reaction. An aspect of the invention is a method of forming a siloxane oligomer product comprising reacting in the presence of a sulfonic acid catalyst: i) at least one silane of the formula:

Si(OR)₄ (I) where R is methyl, with ii) at least one hydrolyzing agent (II) comprising water or a carboxylic acid compound, the reaction being run at a ratio of moles of hydrolyzing agent (II) to moles of silane (I) of from about 0.25:1 to 1.75:1 and for a time sufficient to form an oligomer having no silanol groups thereon.

Another aspect of the invention is a silanol-free polymethoxysiloxane obtained by coequilibration of an oligomer having the average formula: (Si_xO_y (OR)_4x._2y) wherein

R is methyl, and x is 2-6 and 2x>y>0 (so that the silicon content, calculated as Si0₂ % weight, is between 46.5 and 85 %).

Still further aspects of the invention are functionalized products, such as functionalized MQ-, DQ-, TQ-, MDQ-, MDTQ-, and MTQ-type resins, which can be obtained from tetraalkoxysilane oligomers, and methods of their preparation. The individual species in the mixture are characterized by the following general formula: (M₃ + M'_b + M*_c)_2x+y+2 Q_x (T_d + T'_β + T*_f)_y (D_g + D'_h + D*^ in which a+b+c = 1, 0<a< 1, O≤b≤ l, and O≤c≤l; d+e+f= 1, O≤d≤l, O≤e≤ l, and O≤f≤ l; g+h+i = 1, O≤g≤ l, O≤h≤ l, and 0 i< 1; with M', T', and D' containing at least one Si-H functionality with the remander being monovalent hydrocarbon radical having from 1 to 10 carbon atoms, and M*, T*, and D* containing any other combinations of functionalities like alkyl, allyl, vinyl, thioalkyl, epoxyalkyl, etc., where x> 1, y and z are >0, and x, y and z are integers. M is represented by a R₃SiO_l/2unit, wherein R is a monovalent hydrocarbon radical having from 1 to 10 carbon atoms. Examples of radicals represented by R include alkyl radicals such as methyl, ethyl, isopropyl, butyl, hexyl, octyl, etc. M' is represented by a R₂HSiOι_/2 structure, wherein R is defined as above. M* is represented by R*₃SiO_1/2 structures, wherein R* is defined as containing at least one of the following olefinic radicals such as vinyl and allyl, or cycloaliphatic radicals such as cyclopentyl and cyclohexenyl, or aromatic radicals such as the phenyl radical, with the remaining being monovalent hydrocarbon radical having from 1 to 10 carbon atoms. M* can also be replaced by endcapping alkoxy radicals RO_]/2, wherein R is a monovalent alkyl radical like methyl, ethyl, propyl, isopropyl, etc. Q represents a SiO_4/2 structure. T represents a RSiO_3/2 unit, wherein R is defined as above. Similarly, T' and T* are represented by HSiO_3/2 and R*SiO₃,₂ units respectively, in which R* is defined as above. The D units are represented by structures like R₂SiO₂₂, wherein R is defined as above. Similarly, D' is a RHSiO^ and D* is an R*₂SiO_2/2 unit, in which R* is define as above. These formulae represent real molecules, and are not statistical average formulae (like M₀₆Q).

DETAILED DESCRIPTION OF THE INVENTION

Preparation of Poly-Q oligomer

The present invention provides a method for the synthesis of oligomeric polyalkoxy siloxanes by reacting tetramethoxysilane ([RO]₄Si, in which R is methyl) with water and/or a carboxylic acid.

The molar ratio between water (and/or carboxylic acid) and tetraalkoxysilane is from 0.825:1 to 1.75:1. The reaction takes place at room temperature and reaches completion within about one hour. The product is a mixture of linear and cyclic oligomeric alkoxy-capped siloxanes, typically in the range of Si₂ to Sig hen the hydrolysis ratio varies, in a preferred range of, between 1.0.T.0 to 1.1:1.0, with an average molecular weight and viscosity depending on the initial water/carboxylic acid to alkoxysilane ratio. In the preferred range of ratio (1.0:1.0- 1.1:1.0) of hydrolyzing agent to silane, the residual amount of tetraalkoxysilane is less than 0.5 % (GC MS).

The process is catalyzed by strong acid catalysts. Preferred catalysts are lipophilic alkyl or aryl sulfonic acids which provide a good catalytic effect due to their higher solubility in the organic phase. These are very good catalysts not only for the hydrolysis reaction but also for esterification and polycondensation, other key reactions in the overall process. Examples include para-toluenesulfonic acid, benzenesulfonic acid, methanesulfonic acid, trifluoromethanesulfonic (triflic) acid. Another preferred class of strong acid catalysts are strongly acidic ion exchange resins likeNafion^®, Amberlyst^® A-15, A berlyst^® A-18, Bayer^® K-2641, or Purolite^® CT-175 and CT-275, which can be easily filtered off at the end of the reaction, leaving behind a neutral product. The preferred ion exchange resins have both a high concentration of acid sites per gram of resin (typically 4.8 - 5.4 meq/g, preferably 5.2-5.4 meq/g ) and a large pore size (preferably ≥600 μ). The larger pores allow better access of the reagents to the acidic sites resulting in more rapid equilibration. Generally the catalysts are added to the mixture in catalytic amounts (eg., 0.1 to 1 wt %).

The process is particularly beneficial in providing non-toxic and storage stable reactive substitutes for tetramethoxysilane (TMOS).

The initial molar ratio between tetraalkoxysilane and the hydrolyzing agent is carefully controlled to provide a silanol-free oligomer through a fully thermodynamically controlled process. The amount of hydrolyzing agent is below the stoichiometric amount necessary for full hydrolysis, and the hydrolyzing agent is preferably added to the silane gradually with good agitation to achieve rapid distribution of the hydrolyzing agent throughout the reaction mixture. As a result, the oligomer formed has no free silanols and it is fully alkoxy capped, as shown by TR spectroscopy. Free silanols would indicate the formation of a kinetic product, which is prone to gellation over time. In the thermodynamically controlled process of the current invention, all silanols condense to form siloxane bonds.

The carboxylic acids useful herein generally comprise those having the general structure RCOOH or R'(COOH)₂ wherein R is hydrogen or a substituted or unsubstituted alkyl, alkenyl or aryl group, and R' is a substituted or unsubstituted alkyl ene, alkenylene or arylene group. Examples of such R groups include hydrogen, methyl, ethyl, propyl, butyl, butenyl, phenyl, etc. Examples of R' groups include methylene, ethylene, phenylene, etc. Obviously, mixtures of acids may also be used herein. Examples of suitable substituents on the R and R' groups include hydroxy, alkoxy, halo, and thio. Representative examples of suitable acids include formic, acetic, butyric, benzoic, oxalic, adipic, phthalic, maleic, lactic, glycolic, etc. Especially preferred herein is the use of formic acid.

The main by-product of the reaction is the alcohol corresponding to the initial alkoxysilane, or the alcohol and ester corresponding to the carboxylic acid used instead of water. The alcohol and the ester are stripped out by heating to up to about 130°C and applying a slight nitrogen sparge or vacuum. The oligomer is a stable clear viscous liquid, very sensitive to moisture. It is slightly acidic, if a homogeneous acid catalyst was used, or neutral if an acid resin catalyst was used in the hydrolysis. It is essentially free of silanol. Recovery of the desired silicone oligomer from the condensation mixture can be achieved in most instances by a selective distillation procedure. For example, in instances where polyalkoxysilanes are condensed with formic acid or water/formic acid, distillation of methyl formate and methanol can be initially effected from the mixture, followed by the separation, if desired, of various reaction components in order of their volatility.

The product is an oligomeric methoxy capped polysiloxane having an average molecular weight and viscosity directly related to the initial alkoxysilane/water (carboxylic acid) molar ratio. The product has a much lower toxicity than the starting material due to a much lower vapor pressure and lower biomobility. It is a valuable intermediate for making silicas and organofunctional silicas, and as an intermediate for preparing coating formulations, hydrophobicizing agents, fillers, surfactants, antifoam agents, adhesives, etc., as described below.

The oligomeric polymethoxy siloxane has major use as a raw material for the synthesis of functionalized polysiloxanes, for instance highly branched or highly functionalized MQ-, DQ-, TQ-, MDQ-, MDTQ-, and MTQ-type resins. The oligomer retains a high reactivity similar to a silane monomer, and provides a high silicon content, without the burden of toxicity which can accompany the monomer, especially TMOS, use. Acute toxicity and irritation studies indicate a very low order of toxicity following a single peroral dose (LD₅₀ > 2000mg/kg) or skin penetration (LD₅₀ > 2000 mg/kg), moderate eye irritation, and slight skin irritation, in marked contrast to all the toxicological properties of the TMOS starting material. It is also determined that this material would not be classified under DOT's Hazardous Material regulation 49 CFR 171-173. As a result, the oligomer can be shipped under normal conditions, with no HAZMAT special conditions, in contrast to the shipping properties of the TMOS starting material. The oligomer-forming reaction can be conducted at a temperature in the range of from about room temperature up to the boiling point of the alcohol generated in the process (for methanol, about 64°C) for a time sufficient to polymerize the alkoxysilanes. At room temperature the reaction time will typically be from 0.5 to 4.0 hrs. At higher temperatures the reaction time will be shortened.

The reaction may also be conducted in any desired environment such as air, nitrogen, argon, etc. and under any desired pressure. In the interest of process safety, however, it is generally preferred to conduct the reaction under a nitrogen atmosphere at ambient pressure.

The products are relatively polar siloxanes. They may be isolated from acid resin catalyst by filtration and from the alcohol or alcohol/ester byproducts by distillation. The products may also be maintained in the alcohol or alcohol/ester byproducts, or solvents may be added to dissolve the products. Examples of suitable solvents include alkanes, ethers, higher alcohols, aromatic hydrocarbons, etc.

Equilibrations utilizing Poly-Q as a starting material

As previously described, the oligomers of the invention have a wide variety of uses, such as precursors for fumed silica, fused quartz, etc. One particular use is as a precursor of silicone resins, particularly functionalized MQ-, DQ-, TQ-, MDQ-, MDTQ-, and MTQ-type resins. Such resins have previously been reported. However, the oligomers of the invention provide unique opportunity for convenient controlled synthesis of such resins, reacting the oligomer of the invention with a monoalkoxysilane or an optionally functionalized disiloxane. Examples of such resins include equilibration products with hexamethyldisiloxane (MM), producing an MQ resin; equilibration products with divinyltetramethyldisiloxane (M*M*), producing an M*Q resin; and co-equilibration products with M*M* and/or D₄, to compatibilize the product with typical vinyl polysiloxane fluids; and, equilibration products with tetramethyldisiloxane (M'M¹) and M*M*, producing a vinyl and hydrogen functionalized MQ-type resin which is useful, after hydrosilation, for instance in coating, adhesive or sealant applications.

Additionally the oligomers of the invention may be equilibrated with di- or trialkoxyorganosilanes to yield low-volatility, highly functionalized copolymers useful as coupling agents, surfactants and the like, which are of the general structural formulae DQ, TQ, or DTQ resins. Silanes with which the oligomers of the invention may be equilibrated include: alkylsilanes, epoxysilanes,, mercaptosilanes, acryloxysilanes, methacryloxysilanes, vinylsilanes, ureidosilanes, and isocyanatosilanes. Examples of suitable di- or trialkoxyorganosilanes include garnma-glycidoxypropyltrirnethoxysilane, gamma-glycidoxypropylmethyldiethoxysilane, beta-(3,4-epoxycyclohexyl)ethyltrimethoxysilane. 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyl-tris-(2-methoxyethoxy)silane, propyltrimethoxysilane, isobutyltrimethoxysilane, octyltrimethoxysilane, octadecyltrimethoxysilane, 3-butenyltriethoxysilane, 2-(3 -cyclohexenyl)ethyltriethoxysilane, 3-methacryloxypropyltriethoxysilane, 3 -chloropropyltriethoxysilane, 3 ,4-dichlorobutyltriethoxysilane, 3-chIoropropyItrimethoxysilane 3-methacryIoxypropyltrimethoxysilane, methyltrimethoxysilane, octyltriethoxysilane, methyltriethoxysilane, and 3-ureidopropyltrialkoxysilane. Still further equilibration products which may be obtained using the oligomers of the invention result from equilibrations with MM' and/or MD'M followed by hydrosilations with allyl- or methallyl-started polyethers to produce surfactants for polyester type urethane foams; equilibrations with polyether functionalized silicones such as Silwet^® copolymers and other silicone-polyether copolymers to produce compositions suitable for use as surfactants for rigid- and flexible-type urethane foams or for agricultural chemical applications.

The invention is illustrated by the following non-limiting examples. EXAMPLES Example 1

In a typical run, 152.11 grams (1.0 moles) TMOS were placed in a round-bottomed flask with three necks provided with a magnetic or mechanical stirrer, reflux condenser and addition funnel. The acid catalyst (2.6 grams Purolite CT-275 resin) was added to the flask and 19.8 grams of water (1.10 moles) were placed in the addition funnel. The reaction was started by dropwise addition of water to the flask. The reaction was exothermic and the temperature increase (max. 52.9°C) was monitored and recorded. After addition was completed, the temperature decreased rapidly and the mixture was stirred at room temperature for an additional 4 hours. At this point, the product consisted of the oligomer dissolved in methanol and was sampled for GC MS. After filtration of the catalyst, about 159.5 grams of reaction product was transferred to a stripping apparatus. The product was stripped by heating at 130°C with a slight nitrogen sparge, thereby removing about 61.0 grams of lights (methanol) and yielding 97.9 grams of a clear liquid oliogomer product (viscosity 32.7 cSt).

Example 2

Example 1 was repeated using of 2.61 grams of Purolite^® CT-175 as catalyst in place of the CT-275 resin. The reaction yielded 95.8 grams of product together with about 64.1 grams of lights.

Example 3

Example 1 was repeated except that 24 grams (96.0 %, 1.10 moles) of formic acid was used as a hydrolyzing agent in place of water. About 96.1 grams of oligomer product resulted, together with about 65.2 grams of lights (a mixture of methanol and methyl formate about 1 :1 by mass).

Example 4

Example 1 was repeated using a homogeneous acid catalyst (para- toluenesulfonic acid) in a 0.01 molar ratio to TMOS. The temperature during hydrolysis rose to about 64.0°C. After the crude hydrolysis product was stripped, the oligomer product had a pH of 4.0 to 5.0. The product was stable at this pH but attempts to neutralize the product resulted in immediate gellation.

Products as prepared in the previous examples are designated for reference purposes as "Poly-Q". From a chemical point of view, Poly-Q is a mixture of methoxy-capped siloxanes, linears and cyclics, with 2, 3 and 4 silicon atoms, as major components. It is a clear, slightly viscous liquid, and very sensitive to moisture. Left in an open bottle, it gels in a few hours. However, in a dry, closed container it is stable for months. It is a very polar material and it is not miscible with non-polar dimethyl silicones. Because the nature of its siloxane bonds is essentially equivalent to any other siloxane bond, Poly-Q can be equilibrated with other siloxanes or silicones by using a compatibilizing solvent, conferring functionality and compatibility with other silicon- or silicone-based formulations, for a large number of different purposes. One of these purposes is to increase the vinyl content of vinyl endblocked silicone fluids which then can be used to increase the strength of elastomeric compounds without increase in viscosity. This goal can be achieved by using Poly-Q in equilibration reactions with M*M* (divinyltetramethyldisiloxane). In order to make the final product compatible with vinyl fluids, co-equilibration with variable amounts of a diorganosiloxane such as D₄ (octamethylcyclotetrasiloxane) can be practiced. A solvent will generally be needed due to the immiscible nature of Poly-Q in both D₄ and M*M*. The catalyst of choice is the strongly acidic Purolite CT-275. It can simply be removed from the system after reaction by filtration, leaving the product neutral. The choice of solvent depends on its ability to solubilize both Poly-Q and M*M* and D₄. Examples 5-13 illustrate such equilibrations.

Examples 5-13

In a typical run, Poly-Q (31.1 grams, 0.10 moles, as prepared in example 1) was placed in a round-bottomed 3-necked flask equipped with a stirrer, thermometer, distillation head, under a nitrogen blanket. It was dissolved in about 100 grams of solvent (ethanol was used in these examples) and M*M*, D₄ and CT-275 catalyst (about 1 % weight based on the charge) were added. The mixture was heated to reflux for 2 hours under vigorous stirring. After cooling to room temperature, the catalyst was filtered off and the crude reaction product was returned to the flask. The solvent was stripped by heating to 130-140°C (under slight nitrogen sparge). The products were analyzed by GC and the viscosities were determined. The following table contains the major process variables:

A detailed description for a typical equilibration reaction is given for Example #9. The experimental apparatus consisted of a 500 ml round bottomed flask with 3 necks. It was equipped with a stirrer, a distillation head (reflux condenser) and thermometer. A nitrogen blow-by, providing a permanent inerting blanket, was continuously maintained. The following materials were charged to the flask:

Material Amount, g Moles Molar ratio

Poly-Q 62.24 0.20 1.00

M^*M^* 22.37 0.12 0.60

D₄ 1 1.84 0.04 0.20

CT-275 3.94 - -

EtOH 150.12 - _ The mixture was stirred and heated to reflux for about 2 hours. The temperature profile during the equilibration stage was the following:

The reaction mixture was cooled to room temperature. It was filtered using a #4 filter paper and a 5-micron filter pad. The filtrate was a clear, slightly yellow liquid, in one single layer. The weighed amount was 233.05 grams. It was transferred back to the flask for stripping. The stripping was done by stirring and heating to 130-135°C, without nitrogen sparge. The temperature profile during the stripping of lights is shown in the following table:

The stripped product was cooled to room temperature and weighed. The product (91.81 grams) was a clear liquid, in one single layer. The viscosity was determined as 19.0 cSt. From the strip also resulted 141.58 grams of volatile components. Analysis by GC indicated that the volatile components contained 70.4 % EtOH and 18.1% MeOH. Based on GC control runs with Poly-Q, Poly-Q and D₄ equilibrate and Poly-Q and M*M* equilibrate, it was concluded that the equilibration was successful, providing a homogeneous copolymer.

The average molecular weight for Poly-Q used in these examples is considered to be circa 311 Daltons, based on chromatographic analysis, which is the median value between a 2Si and 3 Si methoxy-capped mixture of siloxanes. Starting with this value and the GC result on the lights, it was calculated that an average of 57 % of the initial methoxy groups on Poly-Q underwent transesterification with EtOH. Other Poly-Q species can also be used.

The process described reveals the viability of the equilibration reaction between Poly-Q and functionalized disiloxanes (such as M*M*), as well as any amount of dimethyl siloxanes (specifically D₄). The acidic nature of the catalyst does not affect the outcome of the reaction, other than to cause the desired equilibration of Si-O bonds. In equilibrations with M*M* only, the vinyl level in the product was monitored and compared with the theoretical value. It was found that virtually no loss of vinyl occurs during the equilibration.

The high polarity of the Poly-Q molecules posed a compatibility problem in equilibrations with the generally nonpolar methylsiloxanes. Ethanol was found to be a very good compatibilizing solvent for this process. The ethanol solvent will necessarily result in some transesterification, i.e., replacement of methoxy groups with ethoxy groups, but this is not found to adversely impact the performance of the final product in its further uses. There are always some methoxy groups remaining in the equilibrated product, and their rapid hydrolysis with moisture (where this is desired) suffices to begin a moisture cure (crosslinking of the siloxane bonds) to a degree sufficient to allow completion of cure of the slower hydrolyzing ethoxy groups in due time. If transesterification must be avoided, then an aprotic compatibilizing solvent, such as 1,2-dimethoxyethane (ethyleneglycol dimethyl ether, glyme) must be used. In those cases where ethanol was used as solvent, analysis of the lights by GC found that about 50 % +/- 10 % of the initial methoxy groups are replaced by ethoxy groups. As described above, this does not affect the chemical curing properties of the product. Other dipolar aprotic solvents can also be used.

When the amounts of M*M* and D₄ are small (Examples 5 to 9, Table 1), the viscosity of the product is between 20.0 and 40.0 cSt, consistent with the predominance of Poly-Q in the composition. When the amount of D₄ became significant, the viscosity dropped to single digit values (2.0-4.0 cSt, Examples 10 to 13, Table 1) consistent with the predominance of the dimethylsilicone character. The results reported in Table 1 demonstrate that vinyl functionality can be obtained in a very low viscosity product.

The products resulting from Examples 9 to 13 were compatible with 200 cSt and 2000 cSt vinyl-endblocked silicone fluids.

Example 14 - Equilibration with M'M' and M*M* followed by hydrosilation.

This example illustrates useful products in the area of coatings, antifouling agents, mold release agents, pressure sensitive adhesives, etc. It is known in the art to use vinyl and SiH functionalized silicone fluids for such applications. A typical procedure may use vinyl and SiH endcapped silicone fluids, mixed with MQ resins, in a suitable solvent. Addition of a Pt-based catalyst promotes the hydrosilation reaction. Use of the resulting product usually depends on an additional curing procedure (moisture, UN, thermal initiation, etc.) subsequent to the hydrosilation reaction of this example. The procedure according to this example uses the oligomer Poly-Q, such as prepared in Examples 1-4. This material is equilibrated in situ by adding M'M' and M*M*. At the end, the catalyst is filtered and the product is stripped. The product is a polysiloxane having methoxy, vinyl and SiH functionality attached to the same siloxane backbone. Depending on the final application, it can be treated with Pt in different forms in order to obtain a more or less hydrosilated or dehydrocondensed product. The viscosity of the product can be adjusted based on the ratio of these two types of products. If the product is then exposed to the atmosphere, it cures rapidly due the moisture content of the air (hydrolysis and polycondensation of the methoxy groups). Usually, curing at higher temperature provides a harder coating. TMOS (1.0 moles, 152.3 g) was placed in a 3-necked, roundbottomed flask, provided with a mechanical stirrer, reflux condenser, thermometer, and addition funnel. The catalyst (Purolite CT-275 acidic resin) was added, as a solid, to the starting material (4.75 g). The mixture was stirred while 52.7 g (1.10 moles) of 96%> formic acid was added dropwise from the addition funnel. The temperature increased to about 40- 60 °C, then cooled rapidly. The mixture was stirred an additional 2.0 hours. Without isolating the oligomer, a mixture of M'M' (33.6 g, 0.25 moles) and M*M* (46.6 g, 0.25 moles) were then added from an addition funnel. The system was refluxed for 2 hours, then, after cooling, the catalyst was filtered out. The clear liquid was stripped by heating to 130-140°C. The product was subjected to hydrosilation by adding 10 ppm chloroplatinic acid (CPA) in ethanol. The reaction was rapid, exothermic, with release of hydrogen gas. The product was light yellow with low viscosity (2-10 cSt).

In a similar reaction, using 10 ppm CPA in 1,2-dimethoxyethane as a catalyst, the reaction was less exothermic, and less gas evolved. The product was dark yellow/brown and showed a significant increase in viscosity.

Using Pt-M*M* as catalyst, the hydrosilation was violent, very exothermic, and resulted in a solid product being formed (undesired).

Example 15 - Equilibration with hexamethyldisiloxane (MM).

This example illustrates the synthesis of intermediates and products known as MQ resins. These are very useful materials for a number of different applications: pressure sensitive adhesives, water repellents, surfactants, antifoam agents, silicone rubbers, etc. In a 500 ml 3 -necked, round bottomed flask equipped with a mechanical stirrer, reflux condenser, addition funnel and thermometer, Poly-Q (31.19 g, MW = 311, 0.10 moles) was placed together with MM (4.86 g, 0.03 moles) in 100 g methanol, in the presence of 1.50 g Purolite CT-275 strongly acidic resin. The reaction mixture was heated to reflux (~64°C) under stirring, for 2 hours. Then, 1.8 g (0.1 moles) of water was added slowly from an addition funnel. At the end, the catalyst was filtered, resulting 137.1 g of a M_{0 6}Q resin in methanol. At this point, several options were available. To obtain the solid resin, the crude was simply stripped, removing methanol by heating to 100°C. The product was an off-white solid. If the stripping was done with solvent exchange (e.g. toluene, xylenes, etc.), then the product was a resin solution in the chosen solvent.

Example 16 — Equilibration with M*M*, M'M' and octyltriethoxysilane.

In order to make different Poly-Q equilibrated products more compatible with polymers (e.g. polyolefins), a long alkyl chain can be introduced using octyltriethoxysilane, or other long chain alky ltri alkoxy silanes.

In a typical run, Poly-Q was prepared according to the previous methods, starting with 152.35 g ( 1.0 moles) of TMOS and 52.74 g (1.10 moles) of

96% formic acid, in the presence of the strongly acidic CT-275 resin. At the end of the partial hydrolysis, 23.30 g (0.125 moles) ofM*M*, and 16.79 g of M'M' (0.125 moles), and 34.5 g (0.125 moles) of octyltriethoxysilane were added as a mixture from an addition funnel. The reaction mixture was stirred at reflux for 2 hours, then the catalyst was filtered out. The product was stripped by heating to 135°C. The product was a clear liquid (158.9 g) having a viscosity of 15.7 cSt.

Example 17 — Equilibration with MD'M followed by complete hydrolysis and hydrosilation.

This example illustrates the synthesis of products by equilibration of

Poly-Q with different trisiloxanes. These materials are used as surfactants in ester type polyurethane foaming processes. Poly-Q was prepared in the according to the previous method (Example 16) followed by equilibration with MD'M (222.02 g, 1.0 moles). The equilibration was done at room temperature followed by full hydrolysis, by adding an additional 52.74 g (1.1 moles) of 96% formic acid. The reaction product was cooled and the catalyst was filtered out. The filtrate was stripped by heating to 135°C. It yielded 85.5 g product as a clear liquid. This material was analyzed for Si-H content, resulting 88.7 cc H₂/g. Part of this product (23.4 g) was hydrosilated with an acetoxy capped polyether APEG-550 (76.62 g), in the presence of 10 ppm platinum (0.1 ml 3.3% CPA in ethanol), using toluene as solvent at 91°C. The reaction was very sluggish. After 5 hours and several further additions of the same size aliquots of CPA, the SiH was lowered to 0.3 cc H₂/g. An additional 2 hours of reaction time resulted in trace level of SiH. The product was heated to 137°C and toluene was stripped out. The product weighed 92.6 g and was a brown viscous liquid. It was evaluated in a typical polyester foam test. The product stabilized the foam and the properties were typical.

Example 18 - Equilibration with Silwet^® copolymer.

Silwet copolymers are hydrosilation products prepared by reacting MD_xD'_yM-type siloxanes with polyethers equivalent or analogous to methyl-capped APEG-350. (If MD'M were hydrosilated with methyl-capped APEG-350, the product as sold by Crompton Corporation would be known as Silwet^® L-77). As shown above, fully hydrolyzed equilibration products of Poly-Q with SiH fluids hydrosilated sluggishly with polyethers, because of obvious steric hindrance of the D' units within the Q structures. To circumvent this problem, Poly-Q was equilibrated with the pre-made Silwet copolymer. This approach provides the desired products (MDQ structures with polyether pendants) without the burden of sluggish or incomplete hydrosilation.

In a typical run, Poly-Q was made according to the previous method (Example 16) and then equilibrated with 418.4 g of Silwet^® L-77 (the above-described MD'M trisiloxane hydrosilated with methyl-capped APEG-350 polyether). The equilibration was done without removing the methanol resulting from the TMOS hydrolysis, using 6.75 g of Purolite CT-275 resin as catalyst. The reaction mixture was heated to reflux (64°C) for 2 hours. At the end of the equilibration, a further 52.74 g 96% formic acid was added, in order to complete the hydrolysis of all remaining methoxy groups. The catalyst was filtered out and the solvent was stripped. There was obtained 460.34 g of product as a light yellow liquid, which was tested in polyurethane foams and found to stabilize these systems.

The above examples and disclosure are intended to be illustrative and not exhaustive. These examples and descriptions will suggest many variations and alternatives to one of ordinary skill in this art. All these alternatives and variations are intended to be included within the scope of the attached claims. Those familiar with the art may recognize other equivalents to the specific embodiments described herein which equivalents are also intended to be encompassed by the claims attached hereto.

All published documents, including all US patent documents, mentioned anywhere in this application are hereby expressly incorporated herein by reference in their entirety. Any copending patent applications, mentioned anywhere in this application are also hereby expressly incorporated herein by reference in their entirety.

Claims

CLAIMS 1. A polyalkoxy siloxane oligomer having the average formula: (Si_xO_y (OR)₄. _2y) wherein R is methyl, x is 2-6 and 2x>y >0.

2. An oligomer as in claim 1 further characterized by a hydroxyl content of no more than 0.001% by weight.

3. An oligomer as in claim 1 further characterized by an ambient temperature viscosity in the range of 10 - 500 cSt.

4. A method of forming a siloxane oligomer product comprising: a) reacting in the presence of a sulfonic acid resin catalyst: i) at least one silane of the formula: Si(OR)₄ (I) where R is methyl, with ii) at least one hydrolyzing agent (II) comprising water optionally with a carboxylic acid compound, the reaction being run at a ratio of equivalents of hydrolyzing agent (II), calculated as 2 equivalents per mole of water and 2 equivalents per -COOH group of said carboxylic acid, to alkoxy groups (OR¹) in the silanes (I) and (II) of from about 0.4:1 to 0.75: 1 and for a time sufficient to form an oligomer having no silanol groups thereon in mixture with an alcohol by-product, and, if a carboxylic acid is employed, an ester byproduct, b) separating said oligomer from the catalyst, and said byproducts.

5. A method as in claim 4 wherein said strong acid catalyst is a sulfonic acid or sulfonic acid resin.

6. A method for forming a polyorganosiloxane comprising equilibrating an oligomer as in claim 1 with an alkoxysilane or an optionally functionalized siloxane.

7. A method as in claim 6 wherein said equilibrating step is performed in the presence of an acid catalyst.

8. A method as in claim 6 wherein said oligomer is equilibrated with a member of the group selected from hexamethyldisiloxane, tetramethyldisiloxane, divinyltetramethyldisiloxane and mixtures thereof.

9. A method as in claim 6 wherein said oligomer is further equilibrated with a cyclic diorganosiloxane.

10. A method as in claim 9 wherein said cyclic diorganosiloxane is octamethyltetrasiloxane.

11. A polyorganosiloxane produced by a process as in claim 6.

12. A polyorganosiloxane as in claim 11 which is a co-equilibration product of said oligomer with divinyltetramethylsiloxane and octamethyltetrasiloxane.

13. A polyorganosiloxane as in claim 11 which is a co-equilibration product of said oligomer with divinyltetramethyldisiloxane and tetramethyldisiloxane.

14. A polyorganosiloxane as in claim 11 which is a co-equilibration product of said oligomer with heptamethyltrisiloxane or tetramethyldisiloxane.

15. A polyether functional polyorganosiloxane comprising a hydrosilation reaction product of a polyorganosiloxane as in claim 19.

16. A polyorganosiloxane as in claim 11 comprising a mixture of individual species, the individual species in the mixture being characterized by the following general formula: (M_a + M'_b + M*_c)_2jHyt2 Q_x (T_d + T'_e + T*_f)_y (D_g + D'_h + D*^ in which a+b+c = l, 0≤a< l, 0<b≤ l, and O≤c≤ l; d+e+f= l, 0<d< l, 0<e< l, and O≤f≤ l; g+h+i = 1, 0<g<l, O≤h≤ l, and O<i< l; x> 1, y and z are ≥O, and x, y and z are integers; M is R₃SiO_1/2, wherein R is a monovalent alkyl radical having from 1 to 10 carbon atoms; M' is R₂HSiO_1/2, wherein R is defined as above; M* is R*₃SiOι_/2 wherein R* is a group as defined for R, an olefinic hydrocarbon group, a cycloaliphatic hydrocarbon group, an aromatic hydrocarbon group radical, or M* is an alkoxy group, provided that at least one R* per M* unit is not R; Q is SiO_4/2; T is RSiO_3/2, wherein R is defined as above. T' is HSiO_3/2 T* is R*SiO_3/2, wherein R* as defined as above for M*, other than an R group; D is R₂SiO_M, wherein R is defined as above; D' is a RHSiθ_2/2, wherein R is defined as above; and D* is an R*₂SiO_2/2 unit, in which R* is defined as above for M*, provided that at least one R* per D* unit is not R, and wherein said polyorganosiloxane being an equilibrium product of an oligomer as in claim 1 and at least one silane or siloxane comprising one or more M, M', M*, T, T' T*, D, D'orD* units.

17. A polyether functional polyorganosiloxane comprising an equilibration product of an oligomer as in claim 1 with a polyether functionalized siloxane.

18. An alkoxy functional polyorganosiloxane which is an equilibrium product of an oligomer as in claim 1 with at least one di-or trialkoxyorganosilane.

19. An alkoxy functional polyorganosiloxane as in claim 18 wherein said at least one di- or trialkoxyorganosilane is selected from the group consisting of alkylsilanes, epoxysilanes, mercaptosilanes, acryloxy silanes, methacryloxy silanes, vinyl silanes, ureido silanes, and isocyanato silanes.

20. An alkoxy functional polyorganosiloxane as in claim 18 wherein said at least one di- or trialkoxyorganosilane is selected from the group consisting of gamma- glycidoxypropyltrimefhoxysilane, gamma-glycidoxypropylmethyldiethoxysilane, beta- (3,4-epoxycyclohexyl)ethyltrimethoxysilane. 3-mercaptopropyltrimethoxysilane, 3- mercaptopropyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyl-tris-(2- methoxyethoxy)silane, propyltrimethoxysilane, isobutyltrimethoxysilane, octyltrimethoxysilane, octadecyltrimethoxysilane, 3-butenyltriethoxysilane, 2-(3- cyclohexenyl)ethyltriethoxysilane, 3-methacryloxypropyltriethoxysilane, 3- chloropropyltriethoxysilane, 3,4-dichlorobutyltriethoxysilane, 3- chloropropyltrimethoxysilane 3-methacryloxypropyltrimethoxysilane, methyltrimethoxysilane, octyltriethoxysilane, methyltriethoxysilane, and 3- ureidopropyltrialkoxysilane.