[1]it 396429693 ,Un' ed States Patent Office Patented Feb. 15, 1972 2 (3) at least about 1.5 moles of water for every mole of silane at a temperature of about room temperature to reflux temperature (approximately 25' to 160' C.) for about I to 10 hours to form thereby 5 an organopolysiloxane prepolymer, and (B) separating the resultant prepolyme r product of step A from the reaction mixture to obtain a solventsoluble further curable organopoly siloxane. It is an object of the present invention to provide a 10 method of hydrolyzin g an organic trialkoxysil ane monomer and ultimately preparing a thermoset organopoly siloxane from the hydrolyzed prepolyme r product, the method including (A) h e at in g a m ix tu r e of 15 (1) a silane such as methyltri alkoxysil ane, phenyltrialkoxysilane and rnixtures of phenyltrialkoxysilane and methyltrialkoxysilane; (2) a G r o u p II - A m et al - c o nt ai ni n g h y d r ol y si s c at a20 !yst such as bariu m hydro xide or calciu m hydro xide in an amou nt equiva lent to about 10 to 200 parts by weigh t of Group II-A metal per million parts of silane and water; and (3) at le a st a b o ut 1. 5 m ol e s of w at e r p e r m ol e of 25 silane, at a tempe rature of prefer ably about 75 to 85' C. for at least about one hour to form an organ opolys iloxan e prepol ymer produ ct; and (B) curing the product of step A at about 90' to 300.1 C. or higher for at least about one minute to provide a 30 hard, clear, acetoneresistant thermoset organopoly siloxane. These and other objects will become apparent frorn the specificatio n that follows and the appended claims. The present invention provides a method of hydrolyzin g 35 an organic trialkoxysil ane monomer and preparing a solventsoluble further curable organopoly siloxane prepolyme r therefrom, the method comprising the steps of: (A) h e at in g a m ix tu r e of 40 l(l) a silane which is selected from the group consisting of methyltrialkoxysilane, phenyltrialkoxysilane and mixtures of phenyltrialkoxysilane and methyltrialkoxysilane in which the alkoxy group contains from I to 6 carbon atoms; 45 (2) an effective catalytic amount of a Group II-A metal-containing hydrolysis catalyst such as barium hydroxide; and (3) at least about 1.5 moles of water for every mole of silane at a temperature of about 50' to 160' 50 C. for about I to 10 hours to form an organ opolys iloxan e partial conde nsatio n produ ct prepol ymer; and (B) separating the resultant prepolymer from step A from the reaction mixture to obtain a solvent-soluble fur55 ther curable organopoly siloxane. The present invention also provides a method of hydrolyzing an organic trialkoxysil ane monomer as abovedesc ribed and preparing a thermoset organopoly siloxane from the solventsoluble, further curable prepolyme r by 60 curing the prepolyme r at about 90' to 300' C. or higher for at least one minute up to 168 hours or more to provide a hard, clear, chemical resistant, thermoset organopoly siloxane. The resultant polymers are excehent for making hi.-h temperatur e stable electrical insulation. 65 The preferred Group IIA metalcontaining hydrolysis catalysts are Ba(OH)2 and Ca(OH,)2- Other suitable catalysts are Sr(OH)2 and Mg(OR)2 where R is an alkyl radical of from 1 to 4 carbon atoms and preferably 1 carbon atom. The preferred Group IIA metal has an 70 atomic weight between about 24.3 and about 137.4. Generally, at least a trace amount of the hydrolysis catalyst is necessary to obtain the controllabl e hydrolysis and, 3,642,693 METHODS FOR PREPARING ORGANOPOLYSILOXANES USING GROUP H-A METAL HYDROLYSIS CATALYSTS Amy L. Jasinski, Reston, Va., assignor l@o Owens-Illinois, Inc. No Drawing. Filed Apr. 8, 1968, Ser. No. 719,709 Int. Cl. C08f 11104 U.S. Cf. 260-46.5 R 16 Claims ABSTRACT OF THE DISCLOSURE Methods for hydrolyzing trifunctional organic silanes s@ch as methyltrialkoxysilane, phenyltrialkoxysilane, or mixtures thereof using a Group II-A metal-containing hydrolysis catalyst such as barium hydroxide or calciumhydroxide. The resultant heat curable, solvent-soluble prepolymer is used to prepare excellent laminates, high temperature stable electric insulations, moldings, and hard, clear, flexible coatings. The present invention relates to methods of hydrolyzingmethyltrialkoxysilane, phenyltrialkoxysilane or iii@tu.res of phenyltrialkoxysilane and methyltrialkoxysilane using Group H-A metal-containing hydrolysis catalysts to provide organic golventsoluble, further curable organopolysiloxane prepolymers and thermoset organopolysiloxanes prepared therefrom. @ @In the past, it has been difficult to hydrolyze and condense in a reproducible manner organic trifunctional silanes such as methyl trialkoxysilane, phenyltrialkoxysilane and mixtures of methyltrialkoxysilane and phenyltrialkoxysilane by an acid-catalyzed hydrolysis or a baseca:t,alyzod hydrolysis. The amount of acid catalyst such as hydrochlolric acid or the amount of base catalyst such as potiissium hydroxide employed had to be quite carefully controlled dnd a slight deviation from an exact prescribed amount as a result of an inadvertent mistake or error oftentimes caused a large variation in the polymer product. The reactions of such hydrolysis and condensation are qiiite fast and sensitive and in general they cannot be easily controlled. "Accordingly, it is an object of the present invention tO provide reprodiicible and economical methods of controllably hydtolyzing meth yltrialkoxysilane, phenyltrialkoxysilaiie@ and mixtures of phenyltrialkoxysilane and methylitialkoxysilane omploying Group -II-A metal hydrolysis catalysts siich as barium hydroxide and calcium hydtoxide@ it@ is an object of the present invention to provide a method of controlling the hydrolysis of methyltrialkoxysilane, phenyltrial-koxysilane and mixtures of ph-nyltrialkoxysilane and methyltrialkoxysilane by employing a Group 11-A metal-containing hydrolysis catalyst such as bdrium hydroxide, calcium hydroxide or strontium hydroxide: It is dn object of the present invention to provide a niethod of hydrolyzing methyltriaucoxysilane, phenyltrialkolysilane and mixtures of phenyltrialkoxysilane and methyltrialkoxysilane and preparing a solvent-soluble, further curable organopolysiloxane prepolymer ther6from, the method including (A) heating a mixture of (1) methyltrialkoxysilane, phenyltrialkoxysilane, or a. mixture of phenyltrialkoxysilane and methyltrialkoxysilane in which the alkoxy group has from I to 6 carbon atoms; (2) an effective amount of a Group II-A metal-con@aining hydrolysis catalyst; and
[2]3)642)693 3 hence an amount in the neighborhood of as low as about 0.01 part per million to about I or 2 parts by weight of Group II-A metal per million parts of silane and water can be used to obtain benefits of the present invention. Usually, about 10 to 200 or 250 or 300 parts per million of the Group II-A metal content of the catalyst are used although the preferred range is about 20 to 100 parts per million. The optimum range is about 30 to 60 parts per million. When the amount of catalyst becomes greater than about 250 or 300 parts per million based on the Group II-A metal content of the catalyst, it generally is being used in excess of that needed which is costly. Suitable trifunctional silane starting materials to provide the further curable prepolymers and the cured or thermoset polymers are methyltrialkoxysilanes, phenyltrialk-oxysilanes, or mixtures of methyltrialkoxysilanes and phenyltrialkoxysilanes in which the alkoxy group has I to 6 carbon atoms and preferably 2 to 3 carbon atoms, with the best results beinobtained when the alkOxY group is ethoxy. When a mixture is used, the molar ratio of methyltrialkoxysilanes to phenyltrialkoxysilanes used is generally about 1: I 0 to 1 0: 1, the pref erred ratio being 1: 4 to 4: 1. For general molding, the preferred ratio of the two is about 2:1 and generally for coating applications, good results can be obtained using a ratio of about 1.5:1 to 2.5: 1. A polymer for laminates in particular and also coatings and even flexible coatings caii be made with molar ratios of preferably about 1: 1.0 to 1: 6.0 and more preferably about 1:4. For flexible coating applications, the prepolymers can be dissolved in a solvent, cast and cured in place, to pl,ovide outstanding coatings. In general, solid prepolymers that are tack free at room temperature are prepared by: (1) heating a mixture of (A) a silane that is methyltrialkoxysilane, phenyl trialkoxysilane, or mixtures of methyltrialkoxysilane and phenyltrialkoxysilane in which the alkoxy radical contains from I to 6 carbon atoms and preferably 2 to 3 carbon atoms; and (B) at least a trace of a Group 11-A metal-containin.-- hydrolysis catalyst and at least abotit 1.5 moles of water for every mole of total sitane present, at a temperature preferably of about 65' to 85' C. for a period of time of from about I to about 10 hours; and (II) isolating the siloxane partial condensation product from step I by filtration. The methyl and phenyl copolymers are preferably made by (I) heating a mixture of (A) from about I to about 2 moles of nicthyltriethoxysilane and from about 6 to about I mole of phenyltriethoxysilane; (B) from about 1.5 to about 3 or 4 moles of water for every rnole of total silane present, there being at least a trace of and preferably at least about 20 parts by weight of a Group 11-A metalcontaining hydrolysis catalyst present in the reaction mixture per million parts of water and silane, at a temperature of about 80' C. for a period of time of from about 2 to about 6 hours; and thereafter, the mixture is further processed by (11) filtration from reaction mlxture aiid drying to pi-ovide a free-flowilig powdered solid. The homopolymer from the methyltrialkoxysilane or the phenyltrialkoxysilane is generally prepared by a iiiethod th,,it includes heatin.- under basic conditions i nlixture of 4 (A) a methyltrialkoxysilane or a phenyltrialkoxysilane wherein the alkyl portion of the alkoxy radical contains less than 4 carbon atoms and optionally from 0 to 5 mole perceiit, based on total silane reactant material, of at least a mono-, di-, tri-, or tetraalkoxysitane compound represented by the general formula T T- I Si-OR I 10 T wherein R in the alkoxy radical -OR represents an alkyl radical having less than 4 carbon atoms such as methyl, ethyl and isopropyl, and each T independently represents an aryl, alkyl or alkenyl radical, each of 15 which contains less than 7 carbon atoms, or the aforementioned alkoxy radical, - OR; and (B) from 1.5 to about 10 moles and preferably from 2 to about 4 moles of waterper mole of total silane, said mixture containing by weight from about 10 to 200 20 parts of Group II-A metal in the form of Group II-A metal-containing hydrolysis catalysts such as barium hydroxide, per million parts of total silane and water, the heating of the said mixture to form a siloxane partial condensation product being continued for from I to 10 25 hours at temperatures of at least 50' C. while retaining in said mixture at least 1.5 moles of alkanol by-product per mole of silane starting material assuming complete hydrolysis of all alkoxy-silicon linkages in the liquid reaction mixture. 30 Unless otherwise noted, the viscosity in centipoises used herein is that measured with an RVF Brookfield viscometer in accordance with ASTM 2196-63T, "RheoIogical Properties of Non-Newtonian Liquids." 35 The followin- examples are intended to illustrate the present invention and not to limit the sanic in any way. EXAMPLE I An organopolysiloxane prepolymer was prepared from a purified phenyltriethoxysilane monomer, the monomer 40 b-.ing purified by distillation from an aqueous saturated sodium carbonate solution to about 0 part by weight of HCI per million parts of silane (i.e., no acid) to provide substantially a neutral monomer. The above-described monomer was hydrolyzed with water and a Group 11-A 45 metal-containing hydrolysis catalyst and condensed according to the formulation set forth below: Ingredients Grams Moles P lionyltriethoxysilane ------ - 120 0. 6 50 Water --------------------------- 27 1. 5 Calcium hydroxide ------------- 0.0685 (1) I About 2t4 parts per millioii 011- or about 252 parts per million calciuni per million parts of silane plus water. The above-described amount of purified phenyitriethoxy55 silane was charged into an 800 ml. 3-necked reaction flask equipped with a condenser, mechanical stirrer, thermometer and a Garman take-off. A sattirated CaO solution was added in the amount of 27 grams, this ar)iount of solution containing .0685 gram of calcium hydroxide. The hydrol60 ysis mixture was heated in a preheated oil bath ( 1 20' C.) to about 90-98' C. After 2 to 3 hours of heating, the reaction pot temperature dropped to 79-80' C. At this point the hydrolysis reaction was considered coiiipleted. Thereafter, the reaction produ-.t was isolated by filtration 65 or by stripping off 80-90% of the by-product ethanol (specific gravity .82). The resultant reaction product was added to cold metlianol in a blender and vigorously stirred for several iiiinutes, filtei-ed and dried in a vacuuj-n oven at 60-70o C. A wliite, fltiffy, powdered, furthei70 curable prepolymer was obtained. The yield was close to that of the theoretical yield (64.5 grams). The further curable polymer, which was solvent-soluble and meltible, was put into solution in xylene in iii aiiiount of abotit 48% by wei&,ht of soli(Is aiid the vis75 cosity was about 17 centipoises at 25' C. This xylene soILL-
[3]31642,693 6 tion was used to coat aluminum panels by dipping the panels in the solution. The coatin.-s were hdat-cured at 200-300' C. at a film thickness of about 0.5 mil. Excellent hard, clear coatings were obtained which were acetone resistant. 5 The coatings survived 1% impact elongation tests. The coatings also passed the IOH pencil hardness test and the Scotch Tape test. Laminates were prepared from the solution by dipping Style 181 E-glass cloth in the solution and air drying the 10 dipped cloth for 2 hours. The cloth was then cut into squares 7" x 7"; these were stacked to -ive 14 plies and the stack placed in a press heated to 400' F. Slight pressure was applied tintil the resin gelled (20 minutes) and then 500 p.s.i. for 30 minutes at 400' F. The press was 15 then cooled to 200' F. and the laminate removed. A post cure of 2 hours at each of the following temperatures (110- C., 150- C., 180' C., 205' C., and 230' C.) and finally 12 hours at 2501 C. was given. The resin content of this laminate was approximately 25% by weight. The 20 flexural strength of the laminate was measured at room temperature and was found to be 3 1,000 p.s.i. The tangent modulus at room temperature was 3.1 X 106 p.s.i. The above-mentioned impact elongation tests to determine the impact flexibility of the coatings were made 25 with a G.-E. impact flexibility tester. This instrument generally determines the relative @llexibility of a paint, varnish or enamel film expressed as percentage elongation, in a range of 0.5 to 60% as based on the impact of a solid metal cylinder dropped through a guide track from a 30 height of 4 feet onto the reverse side of a coated test panel. The end of the cylindrical impactor is sttidded with a group of spherical knobs varying in size and calibrated in terms of percent flexibility, based on the elongation or draw they can produce in a metal panel. A reading is 35 made by observing the last indentation in ascending order to show no cracking of the coating. The adhesion of the coating to metal substrate was tested with the Scotch Tape test wherein the tape is uniformly applied to a coated surface which has been cross40 cut @with a razor knife, then pulled off rapidly at 180'. Coatings which exhibit good adhesion do not peel, whereas those not bonded to the substrate peel in the cross-cut area where the coating is not continuous. The 10H pencil hardness test is made by rtibbing a IOH 45 pencil point on the surface with slight pressure for a long enough time to deposit marks thereon. The marks are then rubbed with a tissue or cloth and if no evidence of the marks remain, the coating is deemed to pass the test. EXAMPLE 2 50 A prepolymer was prepared as described in Example I and -filled moldings made therefrom. The prepolymer was dissolved in benzene and the filler in the form of steel fibers (1 6 grams-75 % by weight) was added slowly with 55 mixing, 40 ml. of benzene being used as the solvent. The prepolymer was used in an amount of 4 grams or 25% by weight. Thereafter, the solvent was evaporated and the steel fiber/prepolymer mixture was pressed in a mold at 500 p.s.i. at 350' F. for 2 hours. The pressed mixture 60 was post ctired at 200' C. until a hard disc was obtained. A filled disc of 70,% by weight A1203 powder and 30% by weight of the prepolymer was prepared by pressing in a 5" diameter mold at 400' F. and 2000 p.s.i. for 2 hours. A disc having a thickness of 153 mils was obtained, the (;5 disc having the following properties: Properties: Flexural strength: 5000 p.s.i. Tangent modulus: 0.41 X 106 p.s.i. 70 Compressive strength: 1580 p.s.i. Density: 2.242 grams per cc. Water absorption after 24 hotirs: 0.68% by wei.-ht A filled molded disc of 80% by weigbt of mica and 20% by weight of prepolymer was prepared in a similar 7,5 manner. A good, somewhat hard disc was obtained havin@-, a density of 2.087 grams per cc. and the percent water absorption after 24 hours was only 0.267% by weight. EXAMPLE 3 A phenyl prepolymer was prepared as described in Example I except that 0.010 -ram of calcium oxide was used in place of the saturated calcium hydroxide solution, the amount of calcium oxide used being equivalent to about 42 parts per million OH. The resultant prepolymer has a much lower workable softening temperature in the neighborhood of 100-120' C. instead of 220-240' C. as was the case of the prepolymer of Example 1. The number average molecular weight of the prepolymer was about 2000 as obtained by vapor pressure osmometry. The ethoxyl content of the prepolymer was less than 1% by weight. The total reaction time in this example was 2 hours. Coatings, laminates and moldings were prepared using the resultant prepolymer as described in Examples 1 and 2 and excellent products obtained. EXAMPLE 4 A phenyl prepolymer was prepared as described in Example 1 except that strontium hydroxide was used as a hydrolysis catalyst in place of the saturated calcium hydroxide solution. The following formulation was used: Iiigredients Grams Moles Phenyltriethoxysilane ---------- 240 1 Water --------------------------- 54 3 SrO -------- -------------------- 0. 032 (1) I Equivalelit to about 42 paxts per million OH based on the Nveight of silane plus water. The softening point of the resultant prepolymer was observed to be 110-120' C., the ethoxyl content was less than 1% and the *otal yield was 134.2 grams. The total reaction time for preparing the prepolymer was 2 hours and satisfactory coatings, laminates and moldings were prepared according to the methods described in Examples I and 2. EXAMPLE 5 A phenyl prepolymer was prepared as described in Example 1 usin@ barium hydroxide as the hydrolysis catalyst. The followin@g formulation was used: Iiigredients Grams Moles Phenyltriethoxysilane ---------- 240 Water --------------------------- 54 3 Ba(OH)2.SH20 ----------------- 0.117 (1) I Equivalent to about 0.0617 gram of Ba(OH)2 which is also eqwvalent to 42 parts per million OH. The reaction time was about 4 hotirs and the resultant prepolymer had a softening point of 100-110' C., an thoxyl content of 2-3% and the yield was 135 -rams. The number average molecular weight was 1800 by'vapor pressure osmometry. Satisfactory coatings, laminates and moldings were repared from the prepolymer employid@ the methods p described in Examples 1 and 2. EXAMPLE 6 A phenyl prepolymer was prepared as described in Example 1 except that Mg(OCH3)2 was used as the hydrolysis catalyst in the place of the calcium hydroxide. The amount of Mg(OCH3)2 used was 0.4 gram or 0.00@5 mole. The Mg(OCH3)2 was prepared by reacting magnesiurn filings with methyl alcohol in the presence of iodine. In preparing the prepolymer, the catalyst and silane nionomer were heated together at 90' C. for 30 minutes and then the water was added. The reaction mixture was heated for a total of 6 hours and a white solvent-soluble further curable prepolymer was obtained. The total yield was about 80%. Softenin,,a point of the prepolymer was
[4]7 130-140' C. and the number avera,-e molecular weight was found to be 2500 by vapor pressure osmometry. Excellent coatings, moldin-,s and laminates were prepared as described in Examples 1 and 2. EXAMPLE 7 A copolynier of phenyltriethoxysilane and methyltriethoxysilane was prepared using the methods described in Example I using calcium hydroxide as the hydrolysis catalyst. The molar ratio of phenyl to methyl was 5: 1. The following formulation was used: Iligredieiats Graiiis MOIL'S Plieiiyltrictlioxysil,@ine -------- 240 1 Methyltriethoxysilaiie ---------- 35.6 0. 2 Water --------------------------- 65 3.6 CaO ---------------------------- 0.0203 (1) 1 36 parts per iiiillion OII based on total Nveiglit ofreactauts. The procedure for the cohydrolysis of phenyltrietlioxysilane and methyltriethoxysilane was similar to that described in Example 1. All rea-ents except methyltriethoxysilane were heated to 90-95' C. in an oil bath. After a few minutes the eact temperature b.,@an to drop and when this was be C., the last reagent, methyltrietboxysilane, wa slowly. After 30 minutes, the addition was coinp the reaction was then completed when the pot temi dropped down to 80' C. The polymer was isolated from the reaction n-iixture byfiltration and 149 grams were obtained which compares to a theoretical yield of 142.4 -rams for the formula PhbMeSi6O9 where Ph means phenvl and Me means methyl. The preelired copolymer was soluble in benzene, acetone, xylene, dioxane, dichlorobenzene and other aromat'le and polar solvents. The softenin.- temperature of the polymer was 140' C. and excellent coatings, laminates ,ind moldin@s were prepared as described in Examples 1 and 2. EXAMPLE 8 The methyl/phenyl copolymer was prepared as described in Example 7 except that barium hydroxide was used in the place of calcium hydroxide. The reaction time was between 5-6 hours and a white, solvent-soluble and meltable polymer was obtained. Satisfactory coatings, moldings and laminates were prepared as described in Examples I and 2. As indicated in the above examples, the hydrolysis of phenyltriethoxysilane or mixtures of phenyltriethoxysilane and methyltrietboxysilalie preferably is conducted with about 3 moles of water per mole of silane to provide solvent-soluble, further curable organopolysiloxanes. The prepolymers generally can be cured at about 300' C. for several hours. The following data shows the weight loss from the prepolymers to the completely cured polymers. Percc,iit wt loss to ciiro NN,t. calcul,,ited loss cure at fi,oiri T. G.A. 300' C. for i(P C./iniii. Prel)olyiiik@r Czittilyst 36 hours in air Exanil)lc No.: 6 ------------------- - i\19(OCI13)@, 3.2 ------------- 6-i 4 ------------------- SF(011)2 6.0 6 ------------------- Ba(011)2 S. 3 5:5 I ------------------- Ca(oll), 4.9 6. 2 The saiiiples used in the above table had no further weight loss up to 500 hours, at 3000 C. The T.G.A. test (Thermal Gravimetric Aiialysis) shows the comparative weight loss values for the prepolymers, the results indicatin.- that the degradation begins in the neighborhood of 460-500' C. The softening point of the prepolymer @etierally is in tile i-ange of about 60 or 80' tip to 250' C. and, for the pi-efei-red prepolyjiiers, is zibOLit 100' to 120 or 140' C. 3)642,693 8 As indicated in the examples, the prepolymers are soluble in solvents such as nbutanoll xylene, benzene, dioxane, trichlorobenzene, benzonitrile, dipheiiyl ether, etc. and solutions thereof can be used to prepare excellent coatings. In the above examples, other Group 11-A metal-containing hydrolysis catalysts previously described as suitable can be used for all or part of the hydrolysis catalyst used to provide substantially similar results. In the above worklo in,, examples, the amount of Group II-A metal present in the catalyst was 252 parts per million (p.p.m.) Example 1), 56 p.p.m. (Example 3), 109 p.p.m.,(Example 4), 176 p.p.m. (Example 5), 880 p.p.m. (Example 6), 114 p.p.m. (Example 7), and 143 p.p.m. (Example 8). Also in the 15 above examples, the silane monomers described as suitable can be used in place of all or part of the silane monomers used in the working examples It is to be understood that various modifications of the invention herein described may be made without depart20 ing from the spirit and scope thereof. What is
