CA1310330C - Method for the preparation of methacryloxy and acryloxy containing organosilanes and organosilicones - Google Patents

Abstract

ABSTRACT
This invention relates to an improved process for preparing, purifying and/or storing methacryloxy or acryloxy containing organosilicon compounds without the undesirable polymerization normally associated with the methacrylate bonds. In an alternative embodiment, the process is even further improved with the addition of certain stabilizers, and in particular diketone or ketoester sabilizers.

Description

~L3~ ~3~ -IMPROVED METHOD ~OR PREPARING METHAC~YLOXY
~ND ACRY~OXY CONTAINING ORG~NOSILANES
~ ~ ORGANOSILICO~ES
BACXGROUND OF THE INVENTION
Field of the Invention Thi~ invention r~latQs generally to a ~ovel method for impro~i~g yields in hydrosilation rea~tio~s. More par~icularly, this invention relat~s to a~ improv~d method for preparing me~hacryloxy and acryloxy containing organosilanes and organo~ilicones under certain conditions without th~ u~wan~ed polymerization, i.e., gellation, generally as~ocia~ed with the reactions in~olving these compounds. ~he process is further improved whe~ a stabilizer is used to obviate some of the specific co~ditions required to ~void gellation.
This application is a division of copending Canadian Patent Application Serial No. 526,060 filed April 30, 1987. The claims of the parent application are directed to a process for preparing methacryloxy or acryloxy-containing organosilicon compounds which requires a stabilizer but no post-treatment. The claims of t~is applicati.on are directed to such a process but including a post-treatment step.
Prior Art . . _ The hydrosila~ion reaction, the addition of silicon hydrides to unsaturated ~ompounds, is the most common m~thod ~or the preparatio~ o~
organosilicon compound~ with func~ional groups in ~he organic position o th~ molecules. There are numerous litera~ures which teach how to car~y ou~
hydrs~ilation r~actions with various unsa~urated compounds suc~ as al~enes, un~aturated ethers, amines, ~tc. 1 C. Earborn and R.W. Bott, Organometalli~ compounds o the Grou~ IV Elemen~s (19~8).
Th~se ~ethods, however, ar~ ~o~ suitable ~or the preparation o~ compou~ds containing - 2 - ~ 31~

methacryloxy, CH2~C(CH3)COO-, and/or acryloxy, CH2-CHCOO-, functional groups. This is because, unlike the other organosili~on compounds, methacryloxy and acryloxy cont~ining organosilicon compounds can polymerize easily during preparation and/or purification through reaction of the methacrylate double bonds. Such polymerization not only results in wastçd products, but also renders clean up very difficult, if not impossible, because of the gelled product inside.
U.S. Patent No. 3,258,~77 to Plueddemann et al. teaches ~he preparation of a stable Y-methacryloxypropyltrimethoxysilane by simultaneously charging both trimethoxysilane and allyl methacrylate into a toluene solution containing 2,5-ditertiarylbutylhydro~uinone, additional trimethoxysilane and a solution of chloroplatinic acid all a~ 105C. The use of large amounts of toluene as a solvent, however, makes this process rather expensive and economically unattractive.
In U.S. Patent No. 4,276,426 to Lindner et al., Y-methacryloxypropyltrichlorosilane was again prepared without gellation when trichlorosilane, allyl methacrylate and platinum catalyst were continuously introduced into a pipe-shaped reactor and circulated in the reactor while the reaction mixture was continuously being removed from the reactor. In this reference, the improvement of the process comprised continuously circulating the reaction mixture in the reactor at at lesst 1000 centi~ ~ers per minute. The contents of the reactor will gel when the contents are no~ continually ciroulated, i.~., this proc~ss cannot be carried out as a batch proc~ss.
Thus, there i~ no teachinq i~ the prior art of a process to hal~ the undesirable poly~erization caused by methacryloxy and acryloxy containing organosilicon compounds which process does no~
reguir~ either the use o~ large amounts of solvents or the co~tinuous circula~ion of ~he reaction produ~t mixture. There is a n~ed in the art for a more economic and more expedi~n~ proc~ss for preparing these compound~. Further, there is a need to insure undesirable polymerizatio~ does not occur during preparation, purification or storage of the compounds.
This invention is directed towards the provision of a more economic and more expedient process for preparing methacryloxy and acryloxy containing organosilicon compounds, wherein undesirable polymerization does not occur during the preparation, purification or storage of these compounds.

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BRIEF SUMMARY OF THE INVENTION
Accordingly, this invention relates to a novel process for eliminating undesirable polymerization associated with the acrylate double bonds ~ound in methacryloxy or acryloxy containing organosilico~
compounds. The process eliminates this unwanted polymerization by ~1) combining the contents of a first reservoir containing a methacryloxy or acryloxy containing compound and an inhibitor or inhibitors with a second reservoir containing alkoxy silane or an SiH
containing silicone and a platinum catalyst under appropriate conditions, t2) pos~-treating the reaction produc~ with alcohol and/or a heat treatment, and (3) vacuum distilling the post-treated product.

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The present invention may be practiced as a batch process a~ well as a continuous process.
DETAILED DESCRIPTI02~ OE' THE INVE2tTION
In accordance with the presen~ invention, there is provided a nov~l process for ~liminating undesirable polymerization or gellation which occurs in methacryloxy or acryloxy containing organosilicon eompounds. More specifically it has been found ~hat acryloxypropyltrialkoxysilanes such a~
Y-methacryloxypropyltrimethoxysilane or Y-acryloxypropyltrimethoxysilane can ~e prepared and purified without pol~merization problems when the reactants, trialkoxysilane or SiH containing silicone, allyl methacrylat~ or allyl acrylate and th~ platinum catalyst, are brought together.
The process of the invention comprises the steps of:
(1) charging a first reservoir wi~h a methacryloxy or acryloxy func~ional containing compound and an inhibitor or inhibitors;
(2) charging a second reservoir with an alkoxysilane or an SiH containing silicone and a platinum-containing hydrosilation compound;
(3~ combining the contents of the ~wo reservoirs in a reactor vessel at the appropriate temperature;
(4) post treating t~e crude reaction product with alcohol or post heating the products at the appropriate temperature and for the appropriate time; and (5~ vacuum distilling the pos~-treated products in the presence of inhibitors and under reduced pressure.

- 6 ~ J~s ,s f3 The present inven~ion may be further improved by addition of stabiliz~rs to the first resexvoir containing methacryloxy and acryloxy functional compounds.
The addition of these stabilizers obviate.s the post-treatment step as claimed in the pare~t applicationî the use of these stabilizers also makes th~
system less sensitive to polymerization and thus reduces the quantity of excess methacryloxy and acryloxy functional compound~ which are used when no stabilizers are present to react with unreacted Si-H compounds or unreacted alkoxysilanes and thus halt their polymerization.
The proc~ss of this inv~n~ion can be carried out as a batch or as a continuous process.
This has no consequenc~s with regard to ~he parame~ers of the in~ention except as to how it affQcts the order of combining the reactants.
For example, when the prepara~ion of me~hacryloxy containing organosilicon ~ompound is carried out by a continuous process, the platinum catalyst should be mixed together with the alkoxysilane before combining with the methacrylate or acrylate compound and inhibitor. Thus, the platinum-catalyst can be either dissolved in alkoxysilane and the mixture dropped into the methacryla~e-inhibitor mixture at reaction temperatur~, as in the continuous process, or the platinum catalyst can be added incrementally to the hydrosilation mixture, as when the prepara~ion is carrisd out batYh-wl~e. In any case, one should avoid heating the platinum ca~alyst with the 7 1 3 ~ J

methacrylate-inhibitor mixture to reaction temperature and then dropping in the silane to the platinum-methacrylate-inhibitor mix~ure, because gellation of the reaction mixt~re often results when this mode of addition is used. This latter scenario will not occur if the reservoirs are kep~ separate as indicated by ~he process steps.
It shoula be noted tha~ it is important, in the continuous reaction, to keep the reaction mixture moving all the time in order ~o preclude undesired polymerization from occurring. The continuous unit should also be washed at the end of each preparation with an iner~ solvent such as toluene.
The silanes which can be used in this process may be represented by ~he general formula:
R'nSi(OR)3-n H

wherein R and R' are lower alkyl moieties containing 1 to 20 carbons or more preferably with 1 to 4 ~arbon atoms and n eguals 0 to 1.
The SiH containing silicone of this invention is a polysiloxane polymer with the general formula:
R3SiO[R2SiO]x[RSiO~ySiR3 H

where R is a lower alkyl group having 1 to 8 carbons or an aryl group having 6 to 10 carbons, methyl is the preferred R group, x can range from 0 to 100 and y can range from 1 to 30.
Reactants containing methacryloxy or acryloxy functional groups may be represented by the general formula:

- 8 - ~ J~3 CH2-CCOO(X)mCH2CH=cH2 wherein R2 is hydrogen, a lower alkyl group having 2 to 8 carbons or an aryl group having 6 to 10 carbons, X is CH2CH2O or a CH2 group or a combination of the two groups, and m equals 0 to 10 or, preferably, 0 to 5.
The amount of methacryloxy containing compound, when no stabilizer is used, should always be used in 2 to 10% molar excess over the stoichiometric amount needed to react with the silane or polysilioxane polymer or, preferably, in 3-5~ molar e~cess. As discussed above, the excess use of methacrylate or acrylate components over the stoichiometric required amount will prevent the presence of significant amounts of unreacted alkoxysilanes or Si-H containing polysiloxanes in the crude reaction product.
Inhibitors are used during two stages of the present process: during the hydrosilation reaction and during the vacuum distillation of the post-treated product.
Inhibitors which may be used in either the hydrosilation or vacuum distillation steps of this process include phenolic inhibitors such as monomethyl ether of hydro~uinone ("MMHQ") or Isonox~ 129, aromatic amines such as diphenylendiamine, aromatic sulfur compounds such as phenothiazine (~PTZ") or combinations thereof.
Although both these non-phenolic and phenolic inhibitors may be used during either step, it is preferred to use only phenolic inhibitors, e.g, . .

1 ~ rJ~J~
_ g _ MMHQ, IonolT" or Isonox~ 129 for the hydrosilation reaction step. A combination of both phenolic and non phenolic inhibitors is preferred during vacuum distillation. The concentration of the inhibitor used during hydrosilation varies in the range of 0.2 to 5.0% by weight based on methacrylate or acrylate or, preferably, in the 0.5-2.0% range. For vacuum distillation, the concentration of non phenolic varies in the range of 200 to 10,000 ppm while the concentration of phenolic inhibitor varies from 500 to 15,000 ppm, based on the weight of product used.
The platinum-containing hydrosilation catalyst us~d in the invention may be chosen from the group of supported platinum-catalysts, such as platinum on y-alumina or on charcoal, or from the group of homogeneous soluble platinum complexes such as chloroplatinic acid, bis-(ethylene platinous)chloride, dichlorobis~acetonitrile)platinum (II), cis-dichlorobis(triphenylphosphine)platinum (II), tetrakis(triphenylphosphine)platinum (O) or other soluble platinum comple~es well known in the art.
The soluble platinum complexes are normally in solution in solvents such as isopropanol, acetonitrile or 1,2-dimethoxyethane. The concentration of the platinum catalyst required depends on reaction temperature and time but is generally used in the range of 2 to 100 ppm and preferably 10 to 25 ppm, based on the total weight of the hydrosilane or Si-H containing silicone and allyl methacrylate.
To improve the distillation stability of the crude products in the reaction vessel, the ..

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reactlon mlxture has to b~ post-treated with a small amount of alcohol such ~s me~h~nol and/or heated at sbout 120~C for a period of time. Otherwise, other gellation may occur during the vscuum distillfltion step or during storage or the yield percent of final product may be significantly reduced. The exact reagon why post-treatments $mprove the stability of crude product is no~ known~ But comparison of gas chromatograms taken before or after the post-treatment showed thflt both treatments, alcohol addition or heating at about 120DC, remove the unreacted alkoxysilane or SiH containing silicone left in the mixture AS well as small amounts of by-product.
The smount of ~lcohol required for the post-treatment depends upon the amount sf unreaoted alkoxysllane or SiH containing silicone left in the reaction mixture. Under normal conditions when the hydro~ilation is csrried out to completion, i.e., the alkoxysilane or Si-H containing silicone left unreacted is less than 1% by GC analysis, an ~ddition of 1-3~ of alcohol by weight based on weight of product msde, is enough; although an amount higher than 3% can also be used up until about 5%. Any alcohol, ROH, where R is a 1 to 10 carbon ~tom alkyl group, can be used, but methanol is the most preferred.
Post-trestment requires heating the reaction mixture in the presence of inhibitors at 100-140C for 5 to ~0 minutes, or more preferably at 110-130~C for 20 to 30 minutes.
After the post treatment~s), crude methacryloxy and scryloxy containing org3nosilicon ~31~3~
compounds can be dis~illed in the presence of the ~bove defined inhibitors under reduced pressure.
Accordlng to th~ continuous process of the invention, the meth~crylate/acrylate-inhibitor mixture of the f~rst reservoir should be preheated to 85 to 1~0C or preferably at 90 to 100C. The preheatlng o~ the meth~crylAte will make the temper~ture ~t the point where the react~nts from the two reservoirs meet at 79 to 90C, pre~erably 75 to 85C. The oil bath temperature at which the reactor vessel is kept is best kept at 80 to 120C
or preferably At ~0 to 110C.
When the reaction is carried out in batch, ~he ~irst reservoir can be the reactor itself, the second reservoir sn additional funnel. The reac~ants in the reactor sre slso preheated to 85-100C or preferably ~t 90-100C before the reactants 1n the funnel are dropped in. The preferred reaction temperature is at 80-120C or, more preferably, ~t 90-110C. A reaction tempersture lower than 80~C can slso be used, but the reaction t~kes longer time to run and the unreacted alkoxysilane left in the reaction mix~ure will also be higher. The higher the amGunt of unreacted alkoxysilane remaining in the reaction mixture, the larger the chance the product will gel during distillation und stor~ge if not post treated. Gellstion during hydrosilation may occur when the hydrosilation is carried out at rePction temper2tures sbove 125C.
For both the continuous or the betch process, both residence time of the re~ction mixture .
~ D-14908 _ 12 ~ 3~

and charging rate of reactants depend on the size of the reactor and the temperature of the oil bath used. It is not critical to use specific residence times and/or charging rates. For the continuous process, it is important that the charging rates have to be regulated in such a way that the contents of the reaction mixture, after passing through the continuous reactor, contain little or no unreacted alkoxysilane or Si-H containing silicone and that the mi~ture in the reactor be kept moving all the time.
In another aspect of the invention, as claimed in the parent application, the stability of methacryloxy and acryloxy containing organosilicon compound may be further improved when compounds such as diketone and ketoester are used together with the inhibitor in the first reaction reservoir. Compounds which may be used include almost any compound with 2 oxygen functions such as ketones and esters. Mono keto or ester containing compounds such as mesityl oxide, pentan~ne-2 and methyl propionate also show some stabilizing effec~, but the amount required of such compounds to stabilize the methacrylo~y containing organosilicon compounds toward polymerization will be much higher than those required for diketones and ketoesters.
Diketones such as pentanedione-2,4 and he~adione-Z,5 and ketoesters such as methyl acetoacetate are, therefore, the preferred compounds to be used as stabilizer for the present invention or, more preferably, only the diketones.
The amount of stabilizer used may vary from 2 to 10 per ent by weight based on the amount of . .
~-14908 ~ 3 ~ 3~

methacrylate or acrylate used at the start, and more preferably from 2 to 5 percent.
EXAMPLES
The following specific exsmples ~nd procedures are presen~ed to illustrate the invention, but are not to be construed as 11mlting thereon.
Definitions percent g gram or grams hr hour or hours GC gas chromotography : platinum pl~tinum ~1 microliters ppm p~rts per million Insonox~ 129 a phenolic stabilizer sold under this trademark name and generally available PTZ phenothizine MMHQ monomethyl ethers of hydroquinone ExamPle 1 Using ~ l~boratory unit comprising two reservoirs, A and B, sttached to a reaction vessel ~which was heated with an oil bath, a continuous : preparation of ~-me~hacryloxypropyl~rimethoxy-silane was made ~s follows:

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Be~ore the preparation, the pump used for Reservoir A (allyl methacrylste) was preset to deliver toulene at a r~te of about 2.5-3.0 g/mlnute and the oil bath heated to 110C. Allyl methacrylste, 222 g, and Isonoxm 129, 2.22 g, were mixed ~nd charged ts Reservoir A. When the temperature of the thermocouple reached about 95~C
(at a point where it me~sured the ~emper~ture of allyl methsrryll~te-Isonox~ 129 before the mixture me~ the re~ctants of the second reservoir), ~oluene delivery was stopped ~nd the mixture of allyl methacrylate-Isonox~ 129 was pumped through to the reaction vessel. When most of the toluene in the unit was replaced by allyl methacrylate, trimethoxysilane, 10~ g, was mixed with about 15 ppm of platinum catalyst, H2PtC16, and charged to the unit via Reservoir B. The r~te of trimethoxysilane pumped w~s ad~usted ~irst based on the predetermined ~llyl methacrylate rste to ensure that there was a 3 to 5% mol~r excess o~ the methacrylate. It was further ad~usted when gas chromatographic analysls of the first fraction of product collected showed too much or not enough trimethoxysilsne. The obJective of the adJustment was to obtain a crude ; y-meth~cryloxypropyltrimethoxysilsne mixture contsining no or very little unreacted trimethoxysilane and ~bout 3 to 5% molsr excess allyl methacrylate. The prepar~tion was continued for about 5 hours ~nd 1087 g of crude ~-methacryloxypropyltrimethoxysilane, ldentified ~ by gRS chromotography, were collected. At the end :
~ D-14908 .

.

~ 3 ~ ~ 3~

of the preparation, toluene was again pumped through to wash the system free of the organosilane to preserve the unit for the next preparatlon.
The crude products collected were combined and stabilized with 1000 ppm of phenothiazlne and 500 ppm of monomethyl ether of hydroqulnone. The yield of ~-methacryloxypropyltrimethoxysilane calculAted based on distillation data was 83.9 based on G.C. analysis.
~,æa~
The procedure used for Example 1 was repea~ed five more times. Variations in residence time, reactlon temperature, crude product collected ~nd yield of y-methacryloxypropyl~rimethoxysilane ~re summarized in Table 1.

_ 16 - ~ 3 ~

TABLE I
CONTINUOUS PREPARATION OF
Y-METHAcRyLoxypRopyLTRIMETHoxysILANE

Res~dence Reactlon Grude Product Collected Yield X
No. Tlme.Sminutes) Temp. ~C) Tlme (hr) Welaht (q) ~based on GC~
2 24-28 1~0-106 5.7 1261 85.1 3 24 102-108 2.7 556 71.2 4 20.5 lOS-109 4.8 1037 83 5 17.7 105-108 4.0 1272 85.5 6 18.2 105-108 3.4 1217 ~5.3 .

ExamPles 7 13; Comparative Exam~les A and B
The crude products collected from each experiment were divided and post treated with methanol and/or 120C heating for half an hour prior to distilla~ion. They were then distilled to show the effect of post ~reatmen~. Results obtained are summarized in Table II.
T~BLE Il EFEECT OF POST TREATMENT
Yield %
Post Treatment (based on Obtained from 120C distillation No. Experiment Heatinq MeOH Eroduct) 7 Exp. 2, Table I Yes Yes 82 . 7 8 Exp. 2, Table I Yes No 81.1 Comparative A Exp.2, Table I No No Gelled ~ Exp.2, Table I No Yes ~2.8 .
10 Exp.3, Table I Yes No 69.3 Comparative B Exp.3, Table I No No 42. 7 11 Exp.3, Table I No Yes 70.3 12 Exp. 4, Table I No Yes ~6.0 . . _ 13 Exp. 5, Table I No Yes 80 . g From the above data, it ean be seen that to obtain a uniform distillation stabili~y, the crude product should be post trea~ed wi~h either heat or alcohol prior to di~tillation.

Exæm~le 14 The same procedure o~ Example 1 was ~ollowed except that pentançdione-2,4, 3.4 percent by weight, based on allyl mPthacrylate, was added ~o the mixture of a~lyl methacrylate and Isonox 129. The preparation was carried out for 3.1 hours and 977 g of crude product was col lected . The yield-of Y-methacrylo~ypropyltrimetho~ysilane of the reaction based on GC data was ~5.3%.
Example 15 The same procedure of Example 1 was followed except that pentanedione 2, 4, 3 . 4 percent by weight, based on allyl metharcylate, was added to the mixture of allyl methacrylate-Isonox 129 ~efore it was charged into the unit and the platinum-catalyst used was dichlorobis(acetonitrile)-platinum (II). The preparation was carried out for 3.3 hours and 1036 g of crude product were collected during the period. Yield of reaction based on GC
analysis was 83.4%
ExamPle 16 The same procedure of Example 1 was followed sxcept that the amount of allyl methacrylate was reduced to an allyl methacrylate/trimethoxysilane mole ratio of 0.98 and that pentanedione-2,4, 3.4 percent by weight, based on ally methacrylate, was added to ~he mixture of allyl methacrylate-Isonox 129. The preparation was carried ou~ for 3.5 hours. ~uring the ~irst 1.7 hours, about 15 ppm C12Pt(CH3CN)2 was used as the platinwm catalyst. For the next 1.8 hours, the , ~

platinum catalyst was switched to about 15 ppm H2PtC16. Reaction tempera~ure of the oil bath was 109-113C. The crude product, 555 g, was collected for the first 1.7 hours and 570 g for the ne~ 1.8 hours. GC analysis of the crude products collected using the two platinum catalysts indicated the presence o~ 3.99 and 2.84 area % of unreacted trimethoxysilane, respectively. Yield of the reaction for the first half preparation was 84.8%
and the second half, 84.5% based on G.C. analysis and based on the distillation product produced.
Examples 17-20 The crude products obtained from Examples 14, 15 and 16 were vacuum distilled in the presence of 1000 ppm of PTZ and 4000 ppm of MMHQ without the post treatment. Results obtained are listed in Table III.
TABLE III
VACUUM DISTILLATION OF
Y-METHACRYLOXYPROPYLTRIMETHOXYSILANE
Crude Product(MeO)3SiH Left No.Made fromIn Crude (Area %) Yield %
_ _ I7 14 0~7s 86.9 18 15 1.53 79.5 1916 (lst Half) 3.99 80.5 2017 (2nd Half) 2.84 84.7 From the above examples, i~ can be seen that Y-methacryloxypropyltrimethoxysilane made in ~he presence of pen~anedione-2,~ is more stable than those made in the ahsence of pentanedione-2,4. As a D-1~908 ~ 3 ~

result, ~he ~rude product made in the presence of pentanedione-2, 4 not only can be made with stoichiometric amounts of allyl methacrylate, it can also be distilled without post treatment prior to distillation, ev@n when 2-4% molar excess trimethoxysilane is present.
Example.21 and Comparative Ex~mple C
The pro~edure of Example 1 was followed except that the trimethoxysilane pumping rate was adjusted in such a way that the first ~wo fractions of crude r-methacryloxypropyltrimethoxysilane contained 7-9% molar excess of unreacted ~rimethoxy~ilane and that the remaining fractions collected contained little or ~ra~e amounts of unreacted trimethoxysilane. The fraetions were allowed to stand overnight at room temperature in the presence of 1000 ppm PTZ and S00 ppm MMHQ, based on the weight of product used. Both fractions which contained 7-9% excess unreacted trimethoxysilane (Comparative Example C) gelled overnight, while those fractions which had only little or trace amounts of trimethoxysilane (Example 21) remained as nonviscous liquid. The~e results indicate the effect of unreacted trimethoxysilane in the stability of crude Y-methacryloxypropyl-trimethoxysilane.
Exam~le 22 Into a 1000 ml four-nec~ed round bottom flask, fitted with a mechanical stirrer, an addition funnel, a thermometer and a condenser were added Isonox 129, 2.6 g, and allyl methacrylate, 259 g, . - 21 ~ 13~ 3~

after the flask was flushed with dry air. To the addition funnel was added trimetho~ysilane, 244 g.
The reaction ~ixture was heated to 85C, trimethoxysilane was dropped in and H2PtC16 solution was added:
(MeO)3SiH H PtCl Solution After 1~4 of total added 180 ~1 l/2 180 ~l - total = 650 ~1 (20 ppm platinum) 3/4 160 ~1 End of (MeO)3SiH
addition 130 ~1 During the addition, the mixture was kept at 85-95C
wi~h cold water bath or heating. Heating was stopped when GC of the reaction mixture showed that all of the trimethoxysilane added had reacted.
PTZ, 1000 ppm, and MMHQ, 500 ppm, were added to the reaction mixture and the mixture was heated ~o 120C and kept at that temperature for one-half hour. The experiment was repeated for another five times; none of them showed any instability problems. Yield % of Y-methacryloxypropyltrimethoxysilane all remained in the range of 81-84~ based on G.C. analysis.
ExamPle 23 The procedure used for Example ~2 was followed excep~ that the reaction was carried out on a scale of 1 mole trimethoxysilane and that the platinum catalyst was mixed with trimethoxysilane and ~ropped into allyl methacrylate-Isonox 129 at 90-100C. Yield of Y-me~hacrylo~ypropyltri-- 22 ~ J ci ~

methoxysilane calculated hased on GC analysis was 81.3%.
Comparative Example ~
The procedure of Example 22 was followed except that 112.6 g of allyl methacrylate, 1.12 g of Isonox 129, 108 g o~ trimethoxysilane and 220 ~1 of a H~PtC16 solution (platinum = 15 ppm) were used and that the platinum catalyst was mixed with the allyl me~hacrylate-Isonox 129 mixture and heated to 90C before trimethoxysilane was dropped in.
The experiment was repea~ed five times. Of the five experiments, three of them gelled when approximately B0-85% of the required trime~hoxysilane was added to the reaction mixture.
Yield o~ the other two experiments which did not gel was 66-68% according to ~C analysis of the reaction mixture.
Comparison of Examples 22 and Comparative Example D indicates the importance of the method of platinum-catalyst addition. The platinum catalyst should be reacted with the alkoxysilane prior to its addition to the methacrylate/inhibitor mixture to significantly reduce the chances of gelling.
Example 24 - The procedure of Comparative Example D was followed except that pentanedione-2,4, 3.B g, was added to the allyl methacrylate-Isonox 129~platinum catalyst mixture before the mixture was heated to 90C. The ~xperimen~ was repeated three times but none of them gelled during the D-1.908 ~3 ~ 3 ~-, 3 ~

hydrosilation. Yield of Y-metha~ryloxypropyltri-me~hoxysilane was 65-77~. Furthermore, the three reaction mixtures were also YacUUm dis~illed without the post ~reatment in the pr~senc~ of lO00 ppm PTZ
and ~000 ppm of MMHQ prior to distillation. Yield of Y-methacryloxypropyltrime*ho~silane based on distillation data was 63-74~ ~ased on G.C. analysis.
- Therefore, the addition of pentanedione-2,4 to the reaction mixture has greatly reduced the gellation tendency of ~he Y-methacrylo~ypropyl-trimethoxysilane so that the compound can be made even under those conditions which facilitate the gellation of the said compound, i.e., wh~n the plati~um catalyst is added before the silane or when no alcohol or post-treatment step is used.
Examples 25-29; ComParatie Examples E-K
To test the stability ~ffect of various compounds, a series of experiments was carried out as follows:
Into a 50 ml three-necked round bottom flask, fitted with a condenser, a thermometer and dry air inlet-outlet tubing, were added lO g of distilled Y-methacryloxypropyltrimethoxysilane, 0.0174 g of PTZ, 1.0 or 3.4 g of trimethoxysilane and the desired amount of the tested compound. The mixture was heated to 85C and platinum catalyst was added. Heating was continued and the temperature of th~ reaction mixture was kept at 95-100C. The time when change of viscosity of the reaction mixture was observed was recorded. Results obtained are summarized in Table IV.

- 24 - ~ 3~ 3 It can be seen from the-data that diketones are the most effective compounds to stabilize Y-me~hacryloxypropyltrimethoxysilane against polymerization in the presence of trimethoxysilane and platinum catalyst, or under conditions used for the preparation of methacryloxy-con~aining organosilicon compo~nds. Compounds containing keto-and~or es~er groups also show YariOUS degrees of stabilizing effect (for example, compare Comparative Examples E and F versus Examples 28 and 29 ~d Comparative Examples H-~, but the amounts required for these compounds to prevent the polymerization of metha~ryloxy-~ontaining organosilicon compounds such as Y-methacryloxypropyltrimethoxysilane are much larger tha.n those required when diketone such as pentanedione-2,4 is used.

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Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:
1. A process for preparing methacryloxy or acryloxy containing organosilicon compounds which eliminates undesirable polymerization which process comprises:
(a) charging a first reservoir with (i) 2-10% molar excess of a methacryloxy or acryloxy functional containing compound over a stoichiometric amount of alkoxysilane which would be needed to form a complete reaction between said functional containing compound and said organosilane and (ii) 0.2 to 5.0% of an inhibitor by weight based on the amount of methacryloxy or acryloxy used;
(b) charging a second reservoir with (i) a stoichiometric amount of alkoxysilane needed to form a complete reaction with the methacryloxy or acryloxy containing compound employed in (a); and (ii) a catalystic amount of platinum-containing hydrosilation catalyst;
(c) combining the contents of the two reservoirs in a reactor vessel at 80-120° centigrade;
(d) post treating the crude reaction product with 1-5% alcohol by weight based on weight of product or post heating the reaction product for 5-40 minutes at 100-140°C; and (e) vacuum distilling the post-treated product in the presence of inhibitors and under reduced pressure.

2. The process of Claim 1 wherein the alkoxysilane is represented by the general formula:

wherein R and R' are lower alkyl moiety containing 1-20 carbon atoms and n is 0-1.
3. The process of Claim 2 where the lower alkyl moiety contains 1-4 carbon atom.
4. The process of Claim 1 wherein the methacryloxy or acryloxy functional containing compound is represented by the general formula:

wherein R2 is hydrogen, a lower alkyl group having 2 to 8 carbons or an aryl group having 6 to 10 carbons, X is a CH2 group, and m equals 0 to 10.
5. The process of Claim 4 wherein m equals 0 to 5.
6. The process of Claim 1 wherein the inhibitor is selected from the group consisting of phenolic inhibitors, aromatic amines, aromatic sulfur compounds and combinations thereof.
7. The process of Claim 6 wherein the phenolic inhibitor is monomethyl ether of hydroquinone, Isonox? 129 or Ionol?.

8. The process of Claim 6 wherein the aromatic amine is diphenyl-p-phenylenediamine.

9. The process of Claim 6 wherein the aromatic sulfur compound is phenothiazine.

10. The process of Claim 1 wherein the platinum-containing hydrosilation catalyst is selected from the group consisting of supported platinum catalysts and homogeneous soluble platinum complexes.

11. The process of Claim 10 wherein the supported platinum catalyst is platinum on .gamma.-alumina or charcoal.

12. The process of Claim 10 wherein the homogenous soluble platinum complex is selected from the group consisting of chloroplatinic acid, bis(ethylene platinous)chloride, dichlorobis(acetonitrile)platinum (II), cis-dichlorobis(triphenylphosphine) platinum (II) and tetrakis(tetraphenylphosphine)platinum (O).

13. The process of Claim 12 wherein the soluble platinum complexes are used as solution in solvents.

14. The process of Claim 13 wherein the solvents are isopropanol, acetonitrile or 1,2 dimethoxyethane.

15. A process for preparing methacryloxy or acryloxy containing organosilicon compounds which eliminates undesirable polymerization which process comprises:

(a) charging a first reservoir with (i) 2-10% molar excess of a methacryloxy or acryloxy functional containing compound wherein R2 is hydrogen, a lower alkyl group having 2 to 8 carbons or an aryl group having 6 to 10 carbons, X is a CH2 group, and m is equal to 0 to 10, which excess is over a stoichiometric amount of alkoxysilane which would be needed to form a complete reaction between said functional containing compound and said organosilane and (ii) 0.2 to 5.0% monomethyl ether of hydroquinone, Isonox? 129 or Ionol? by weight based on the amount of methacryloxy or acryloxy compound used;
(b) charging a second reservoir with (i) a stoichiometric amount of an alkoxysilane wherein R and R' are lower alkyl moiety containing 1 to 20 carbon atoms and n is 0, which alkoxysilane is needed to form a complete reaction with the methacryloxy or acryloxy containing compound employed in (a); and (ii) a catalytic amount of platinum-containing hydrosilation catalyst selected from the group consisting of supported platinum catalysts and soluble platinum complexes;
(c) combining the contents of the two reservoirs in a reactor vessel at 80-120° centrigrade;
(d) post treating the crude reaction product with 1-5% alcohol by weight based on weight of product or post heating the reaction product for 5-40 minutes at 100-140°C; and (e) vacuum distilling the post-treated product in the presence of phenolic or nonphenolic inhibitors under reduced pressure.
16. A process for preparing methacryloxy or acryloxy containing organosilicon compounds which eliminates undesirable polymerization which process comprises:
(a) charging a first reservoir with (i) 3-5% molar excess of a methacryloxy or acryloxy functional containing compound wherein R" is hydrogen, a lower alkyl group having 2 to 8 carbons or an aryl group having 6 to 10 carbons, X is a CH2 group, over a stoichiometric amount of alkoxysilane which would be needed to form a complete reaction between said functional containing compound and said organosilane; and D-14908-C-l (ii) 0.5 to 2.0% monomethyl ether of hydroquinone, phenothiazine, or diphenylenediamine inhibitor by weight based on the amount of methacryloxy or acryloxy used;
(b) charging a second reservoir with (i) a stoichiometric amount of alkoxysilane wherein R and R' are lower alkyl moiety containing 1 to 4 carbons and n is 0 to 1 which alkoxysilane is needed to form a complete reaction with a given methacryloxy or acryloxy containing compound and (ii) 2 to 20 parts per million of platinum on .gamma.-alumina or charcoal;
(c) combining the contents of the two reservoirs in a reactor vessel at 80-120° centigrade;
(d) post treating the crude reaction product with 1-3% alcohol by weight based on weight of product or post heating the reaction product for 20-30 minutes at 100-140°C; and (e) vacuum distilling the post-treated product in the presence of phenolic or nonphenolic inhibitors or diphenylenediamine and under reduced pressure.

17. A process for preparing methacryloxy or acryloxy containing organosilicon compounds which eliminates undesirable polymerization which process comprises:
(a) charging a first reservoir with (i) 3-5% molar excess of a methacryloxy or acryloxy functional containing compound wherein R" is hydrogen, a lower alkyl group having 2 to 8 carbons or an aryl group having 6 to 10 carbons, X is a CH2 group, over a stoichiometric amount of alkoxysilane which would be needed to form a complete reaction between said functional containing compound and said organosilane; and (ii) 0.5 to 2.0% monomethyl ether of hydroquinone, Isonox? 129 or Ionol?
inhibitor by weight based on the amount of methacryloxy or acryloxy used;
(b) charging a second reservoir with (i) a stoichiometric amount of alkoxysilane wherein R and R' are lower alkyl moiety containing 1 to 4 carbons and n is 0 to 1 which alkoxysilane is needed to form a complete reactlon with the methacryloxy or acryloxy containing compound employed in (a); and (ii) 2 to 100 parts per million of homogeneous soluble platinum complex selected from the group consisting of chloroplatinic acid, bis-(ethylene-platinous)chloride, dichlorobis(acetonitrile)platinum (II), cis-dichlorobis(triphenylphosphine) platinum (II) and tetrakis(tetraphenyl phosphine)platinum (O);
(c) combining the contents of the two reservoirs in a reactor vessel at 90-120° centigrade;
(d) post treating the crude reaction product with 1-3% alcohol by weight based on weight of product or post heating the reaction product for 20-30 minutes at 110-130°C; and (e) vacuum distilling the post treated product in the presence of phenolic or nonphenolic inhibitors under reduced pressure.

18. The process of Claim 17 wherein the homogeneous soluble platinum complex is used as solution in solvents.

19. The process of Claim 18 wherein the solvent is isopropanol, acetonitrile or 1,2 dimethoxyethane.

20. A process for preparing, purifying and/or storing methacryloxy or acryloxy containing organosilicon compounds which eliminates undesirable polymerization which process comprises:
(a) charging a first reservoir with (i) 3-5% molar excess of a methacryloxy or acryloxy functional containing compound wherein R" is hydrogen, a lower alkyl group having 2 to 8 carbons or an aryl group having 6 to 10 carbons, X is a CH2 group, (ii) 0.5 to 2.0% monomethyl ether of hydroquinone, Isonox? 129 or Ionol?
inhibitor by weight based on the amount of methacryloxy or acryloxy used; and (b) charging a second reservoir with (i) a stoichiometric amount of alkoxysilane wherein R and R' are lower alkyl moiety containing 1 to 4 carbons and n is 0 to 1 which alkoxysilane is needed to form a complete reaction with the methacryloxy or acryloxy containing compound employed in (a); and (ii) 2 to 100 parts per million of homogeneous soluble platinum complex selected from the group consisting of chloroplatinic acid, bis-(ethylene platinous)chloride, dichlorobis (acetonitrile)platinum (II), cis-dichlo:robis(triphenylphosphine) platinum (II) and tetrakis(tetraphenyl phosphine) platinum (0);
(c) combining the contents of the two reservoirs in a reactor vessel at 90-120° centigrade;
and (d) vacuum distilling the product in the presence of phenolic and nonphenolic inhibitors and under reduced pressure.