CA1091380A

CA1091380A - Polymerization of silanes

Info

Publication number: CA1091380A
Application number: CA246,676A
Authority: CA
Inventors: Mark W. Siefken
Original assignee: Minnesota Mining and Manufacturing Co
Current assignee: 3M Co
Priority date: 1975-03-07
Filing date: 1976-02-26
Publication date: 1980-12-09
Also published as: DE2609150C2; FR2303040A1; DE2609150A1; GB1546888A; IT1064112B; FR2303040B1; JPS5311559B2; JPS51112899A

Abstract

ABSTRACT

The polymerization of silanes and siloxanes in the presence of water is found to be catalyzed by highly fluorinated aliphatic sulfonic and sulfonylic catalysts.

Description

~ 912,209 lV~

RAPIDLY CURABLE SILOXANE COMPOSITION

There are many different types of silicone con-taining compounds which are known to be polymerizableO
Those materials which are polymerizable into molecular chains of greater size than that of two monomers (i.e. a dimer) require at least two labile groups, groups that : can split off during a polymerization ^reactionO This allows the residue of the monomer (the monomer or reactant less the labile group) to react through the reactive site formed by the elimination of the labile group, to another reactive site on another monomer. With only two such labile groups on the monomers, essentially linear poly-mer chains will be formed in the polymer product unless additional, three-dimensional reactants (crosslinking - agents) are added to the reaction mixture. With three --` s~l I co~
: W or more labile groups on the ~illcone atom or with mono-mers having two terminal 5i 11 conc atoms with at least three labile groups between them, crosslinking can occurO
sI l~o~
;~ A typical polymerization reaction of a sillconc containing monomer would be that of dichlorodlmethyl-- 20 silane in an aqueous phaseO Hydrogen chloride evolves, chlorine being released from the monomer and hydrogen being removed from the water. This can readily be seen by the drop in pH of the solution and the odor of hydro-chloric acid. A second phase will develop ln the solution,

2~ a light, colorless oil comprising a mixture of linear and cyclic poly~dimethylsiloxanes~ of empirlcal composition:
i [(CH3)2SiO]n where n is an integer greater than 20 In this simple reaction, n can be equal to several hundred.
Various techniques are known for controlling the hydrolysis reaction. In order to increase the propor-tion of low molecular weight molecules, a cosolvent for organochlorosilanes and water can be used. Reduced temperatures and hydrolysis in the presence of water-immiscible, non-polar solvents minimlzes the formation of polysiloxanes. Strong acids favors the formation of low molecular weight cyclic polymer unitsO Silanols are ~-stabilized in nearly neutral solutions and preferentially ; condense to siloxanes in the presence of strong bases.
.. , . S ~
D In general, it is known that riliconc materials of the general formula:
i R4_m wherein X is a labile group, R is a hydro-carbyl group and m is an integer 2, 3 or 4, are polymerizable by various techniques~ By labile group is meant any hydrolyzable group and hydrogen. A hydro-carbyl group is a moiety connected through a carbon atom to the silicon.
Exemplary labile groups, X, are alkoxy, aryloxy, acyloxy, halogen and hydrogen. These groups may contain heteroatoms and may be linear, branched or cyclic as long as the group is hydrolyzableO

The term hydrocarbyl is intended to include groups resulting from the removal of hydrogen from the carbon atom of a hydrocarbon and from hydrocarbons con- -taining one or more heteroatoms selected from oxygen, sulfur and nitrogen. Exemplary hydrocarbyl groups include aromatic groups containing one to ten carbons (e.g., phenyl, naphthyl, and benzothienyl) and aliphatic - groups containing 1 to 18 carbon atoms. The aliphatic groups may be linear, branched or cyclic (e.g. methyl, ethyl, isopropyl, propyl, cyclohexyl, octyl, dodecyl, octadecyl, ethoxyethyl, ethoxyethoxyethyl, thioethoxy- -~
ethyl, tetrahydrofuryl, tetrahydrothienyl, dioxanyl, piperidinyl, pyrrolidinyl, etc. The hydrocarbyl group may be substituted by functional or non-functional 15 groups such as halogen, alkoxy, epoxy, phenoxy, cyano, - -vinyl, allyl, acryloxy, and the like.
Exemplary classes of compounds falling within the general formula are silanes, silanols, siloxanes, - alkoxy silanes, aryloxysilanes, acyloxysilanes, halo-alkylsilanes, haloarylsilanes, etc. It is generally well known that almost any conceivable functional group can be introduced into the side chain of an alkyl or -~ -aryl-substitued silane, so that a detailed description .
of operational substltuents is unnecessary.
Specific compounds falling into the broad class of polymerizable silicon materials are, for example: -( 3)3 3 CH351(0CH3)3

-3-. .
.

, . ~ ~

l.V~

:~ CH3si~.c6Hl3)3 (CH3)2Si(OC2H5)CH CH2 ~ OC(CH3)2 (CH3)2Si~ ¦
OC~CH3)2 NH2(CH2)3si~Oc2H5)3 CH3Si~C6H5) ~OC2H5)2 ~` HC~CH2)3Si~OCH3)3 . ~NC5H4)SicH3~0c2H5)2 H3C-CH2-0-CH2-CH2-SiCH3(0C2H5)2 ~ Si~OCH3)4 `.; 10 (CH2=CH-CH2)2Si(OCH3)2 ~`

.

t.'`

; '' -~' ~. - 4 -. .

:

1~3~

It is also known that polymers havlng at least one labile-group-substituted-silyl group, SiXm, may be cured by various techniquesO
Exemplary curable silyl-substituted polymers are the silicone terminated polyurethanes described in U.S. Patent NoO 3,632,557 (page 5, line l8-6, . line l3).
: Specific examples of a silyl-substituted poly-mer have the structures:

CH3 ,, C ~ H-CO-NH(CH

CH2-CH - 0)5l 7 C - NH ~ ~i(OC2H5)3 R ~ 3 O-C-NH ~
NH-co-NH-(cH2)3si(OC2H5)3 O O O
~- ~ C-(CH2)5C-OCH2-CH2 ~ C-NI ~
NH-CO-NH-. (CH2~Si (OC2H5)3 o-CH2-CH20-C-NH ~
NH-CO-NH(CH2 ~ i(0C2H5)3 ` ` 109i~3V

This invention relates to the use of a novel class of catalyst for use in polymerization of a silicone material.
Specifically this invention relates to the use of highly fluorinated aliphatic sulfonylic and sulfonic catalysts for the polymerization of silicone ` materials.
Accordingly, the invention provides a method of curing at least one silane compound selected from monomers and polymers of the formula XmSiR4 m wherein X is a labile group, R is a hydrocarbyl group resulting from the re-moval of a hydrogen atom from the carbon atom of a hydrocarbon or a hydrocarboncontaining one or more heteroatoms selected from oxygen, sulfur, and nitrogen and m is 2, 3 or 4 comprising curing said at least one silane compound by placing said compound into catalytic proximity with a catalytically active amount of a highly fluorinated aliphatic sulfonylic catalyst comprising at least two highly fluorinated aliphatic sulfonyl groups attached directly to an imide or methylene group, and water.
A preferred group of silane compounds are epoxy-terminated silanes selected from . _ _ CH2--CH~R6~n Si~oR7~m (4-m) and [ ~ ~ (4-m) wherein each R6 is independently a divalent hydrocarbon radical of less than 20 carbon atoms, or a divalent radical of less than 20 carbon atoms the back-bone of which is C atoms which may be interrupted by individual atoms from the group of N and 0, and 0 atoms in the form of ether linkages, m is 2 or 3, n is 0 or 1, and R7 is an aliphatic hydrocarbon radical of less than 10 carbon D

atoms, or an acyl radical of less than 10 carbon atoms.
~ Alternatively, the silane compound may be a copolymer of a polymer-- izable organic vinylic compound with 0.01 to 100 moles per 100 moles of organic vinylic compound of a vinyl trialkoxysilyl monomer of the general formula R8-C=CH
~ 2 R9-Si(OR)3 wherein R8 is hydrogen, methyl, or chlorine; and R9 is a divalent radical sel-ected from the group including , /

~ , R10-, and-C O R10 wherein R10 is a lower alkylene group having 2-6 carbon atoms.
m e sulfonylic materials are defined as a compound containing two highly fluorinated aliphatic sulfonyl groups attached directly to an imide or methylene, e.g., -NR'- or CR'R". The sulfonylic catalysts may be partially represented by the formula (RfSo2)-Q-(so2Rft) wherein Rf and Rf' are independently highly fluorinated aliphatic groups and Q is a divalent radical selected from -NR', -CR'R" and -C=CHR3 wherein R' is selected from hydrogen, chlorine, bromine iodine, ammonium cation and metal cation, R" is selected from hydrogen, chlorine, bromine, iodine, RfS02, alkenyl of 3 to 4 carbon atoms, aIkyl of 1 to 20 carbon atoms (preferably 1 to 4), aryl of up to 20 carbon atoms (preferably 1 to 10), and alkaryl of up to 20 carbon atoms (preferably 7 to 10), R3 is H, alkenyl of 3 ~; to 4 carbons and aryl of up to 20 carbons, .
:...
. .

- 6a -i~ iD

~i .

~3~

and R' is selected from hydrogen, chlorine, bromine, iodine, ammonium cations or metal cations.
m e catalysts wherein the N or C atom bonded to the highly fluorinated aliphatic (preferably alkyl) group has a hydrogen atom bonded thereto are active catalystsO Those having no hydrogen atom are latent and may be activated by heat, acid, chelating agent or combinations thereof as later exemplified.
Metals useful in the above definitions essen-tially includes all metalsO All metals inclusive of and to the left of aluminum, germanium, antimony and polonium on the periodic chart of the elements, and the rare earth metals can function in the practice of this invention.
The group Ia and IIa metals must be activated by acids and heat or chelating agents and heat, but they are functional. Examples of many metals, including lanthanum, are provided to show that all metals will work, even though some would be commercially useless because of expense. Preferably the metals would exclude elements 59-63, 65-71, and those above 89.
According to the Periodic Table in Advanced Organic Chem_str~, Cotton and Wilkinson, 2do Edo~
Interscience publishers, 1966, more preferred metals woul~
be those of Groups, Ia, IIa, VIa, VIII, Ib, Ilb, IVbg and Vb and lanthanum, titaniuma zirconium, chromium9 molybdenum, manganese3 cesium, and gadolinium based on economic considerations.
In the practice of this invention9 Rf and R9f are independently defined by highly fluorinated aliphatic .
: ~ 7-V

radical which encompasses fluorlnated, saturated, mono-valent, aliphatic radlcals havlng 1 to 20 carbon ato~s.
The skeletal chain of the radical may be straight, branched or, if sufficiently large (e.g. at least 3 or 5 atoms) . 5 cycloaliphatic, and may be interrupted by dlvalent oxygen atoms or trlvalent nltrogen atoms bonded only to carbon atomsO Preferably the chain of the fluorinated aliphatlc radical does not contain more than one hetero atom, iOeO, nitrogen or oxygen, for every two carbon atoms in the skeletal chainO ~ fully fluorinated group is preferred, but hydrogen or chlorlne atoms may be present as substl-tuents ln the fluorinated aliphatlc radical provlded that not more than one atom of elther ls present ln the radlcal for each carbon atomO Preferably, the fluoroallphatic . 15 radlcal is a saturated perfluoroalkyl radical havlng a skeletal chain that ls straight or branched and has a -: formula CXF2X+
whereln x has a value from 1 to 1~.
- . 20 Ths preferred actlve catalysts of thls invention . are those compounds havlng the formula (RfS02)Q(02SRf) . wherein Rf and Rf are lndependently a hlghly fluorlnated alkyl group, and . 25 Q is a divalent radlcal selected from -NH- and -CHR-wherein R is selected from Br, Cl, I, H, alkyl groups of 1 to 20 carbon atoms, alkenyl of 3 to 4 carbon atoms, aryl or aralkyl of up to 20 carbon atoms, or R'X, ., .

' . .
', ' ~ 't.1.~.3~

wherein R' is an alkylene group of up to 20 carbon atoms and X is H, Br, Cl, I, -O2SRf, -CH(O2SRf)2, -fH-(CH2)n-COOR , or -CY(COOR )2 Br wherein R is H or 1 to 8 alkyl and n is 0 to 5 8, and wherein R2 is alkyl of 1 to 4 carbon atoms or phenylalkyl, the alkyl group of which has 1 to 4 carbon atoms, and Y is H, Br, C], I, or NO2.
These catalyst compounds are known in the art, although not for the cure of epoxy-terminated silanes ` into abrasion resistant coatings. Prior art disclosure of the sulfonic acids, sulfonylic acids and their derivatives is disclosed in such materials as U.S.
Patents 3,586,616; 3,632,843; 3,704,311; 3,758,531;
3,758,591; 3,758,592; 3,758,593; 3,776,960; 3,794,687;
3,842,019; 3,932,526; German D.S. 2,239,817.
The curable compositions of this invention can be modified by incorporating therein any number of conventional fillers, e.g., reinforcing fillers such as 20 finely divided silica, non-reinforcing fillers such as coarse silicas, diatomaceous earth, metallic oxides such as titania, _g_ :' .

,:
i.' . . . ~
- . .
. . .

ferric oxide, zinc oxide, talc and the llke, and fibrous fillers such as asbestos or glass fibers or filaments.
The fillers are added in proportlons up to about 200 percent by welght of the curable composltlon, preferably up to about 50 percent.
The vulcanizable compositions of the invention may also contaln modlfiers such as reslnous slloxane modlflers, plasticlzers, pigments~ UV stabilizers, oxidatlon lnhlbitors, and dlelectric substances such as gr~phite or carbon black.
EXAMPLES
-:

To 100 parts of dimethyldlmethoxysilane was added 1 part of bls(trlfluoromethylsulfonyl)methane. The mixture was stlrred to dlsperse the catalyst and allowed to stand at room temperature (24C~. After 24 hours (no - YiSco~S
~_) further change occurred ln 4 days) a V1OOUOUB material (vlscosity greater than about 1,000,000 centlpoise) was obtained.
Slmilar results were obtained when either bis(perfluorobutylsulfonyl)methane, bis(trlfuloromethyl-sulfonyl)imide, trlfuloromethylsulfonic acld or methyl

4,4-bls(trlfluoromethylsulfonyl~-2-carboxy-2-bromobutanoate was used in place of bls(trifluoromethylsulfonyl methane.
When 5 percent by weight of tetramethylslllcate and 2 percent by welght of tin octoate is added to the above-described vlscuous flulds, the mlxture cures to a rubbery product havlng good tensile strength and elongation.
When the above experlments were repeated using varlous amounts of catalyst, it was found that simllar . .

: - !-:' .

results were obtained when from about 0.05% to more than ~`;

5% by welght of catalyst was used.

Into 100 parts of vinyltriethoxysilane was mixed 1 part of bis(trifluoromethylsulfonyl~methane and the mlxture was coated onto polyethyleneterephthalateO In one day a coherent film had formed which could be stripped from the substrate as a self-supporting film was obtained.
When the mlxture was coated onto polyethyleneterephthalate primed with polyvinylidenechloride, a tenatiously adherent film was obtalned that had water repellent characteristics~
When the example was repeated using as catalyst 1 part of trifluoromethylsulfonic acid, the coated mixture cured ln about 4 hours.
Similar results were obtained wlth other highly ` fluorinated alkylsulfonyl protonic aclds.
, EXAMPLE 3 ~ .. = .. ........
, Example 2 was repeated usin~ 3(methacryloloxy) propyltrimethoxysilane in place of vinyl trlethoxysilane.
In one day a tacky film was obtained (it did not change on standing an additional 3 days)O On exposure to the radiation of a Hanovia lamp for 2 minutes an adheslve film was formed which performs as an excellent ~dheslve for polymethylmethacrylateO

Example 2 was repeated using vlnyl triacetoxy-silane. In one day tno further change in 4 days3 a friable - brittle film was formed when 1% bis(trifluoromethylsulfonyl~
methane was used as catalyst. When 1% trifluoromethyl-sulfonic acid was used as catalyst~ a f'riable film was "'' ~ 3i~

obtalned in 4 daysO The film had water repellent propertlesO

Example 2 was repeated using perfluorolsopropoxy-propyltriacetoxysilane in place of vlnyltriethoxysllane.
A tenatious hlghly water repellent film was formed, Example 2 was repeated using phenyltrlethoxy~
silane in place of vlnyltriethoxysilane5 A friable film was obtained for coatings of about 25 microns ln one day and in 4 days for coatins 100 microns thlck. Slmllar results were obtalned when each of bls(trifluoromethyl-sulfonyl)methane and trifluoromethylsulfonic acid were used as catalyst.

Example 1 was repeated using-in place of 100 parts of dlmethyldimethoxysilane a mixture of 90 parts of dimethyldimethoxysilane and 10 parts of vinyltriethoxy tr~ ro ~thYISul~ nYI
B silane and 1 part of bis(tri~luoromcthy~fulDony~)methane as catalystO A viscuous gum-like material (viscosity greater than 1,000,000 centipoise) was obtained. Similar viscuous material was obtained when trifluoromethylsulfonic acld was used as catalyst.
Two percent by weight of lauroyl peroxide and '~ 10 percent by weight of calclned magnesium oxide was added to the material and the mixture milled on a rubber mill for about 10 minutesO The mixture was sheeted from the mill and heated at about 1 hour~ There was obtained a rubbery product having good tensile strength and elongationO

A trialko~ysilyl-endcapped polymer was prepared -.
. .

10'31 ;~f~V

from polyoxypropylene glycol (molecular welght of 3000), toluene dilsocyanate, and r-amlnopropyltriethoxysilane was added theretoO To 100 parts of this polymer was added 1 part of bis(trifluoromethylsulfonyl)methane in 15 ml.
of methylene chloride while stirring vlgorously. In 1 to 2 hours the mixture had cured to a tough rubbery productO
EXAMPLES 9 - ?
The following group of examples demonstrate the generic utllity of catalysts according to the present inven-tion in curing of silane monomers.
To lOoO g portions of Si(OCH2CH3)4 was added 0.5 , g of the following catalysts:
9. (CF3S02)2CH2 10. (CF3S02)2CHC6H5 11. (CF3S02)2CHCl 12. (CF3S02)2CHBr ; 130 (CF3S02)2CHcH2cH(cF3s02)2 14. (CF3S02)2CHcH2,c(c02c2H5)2 Br 15. (CF3S02)2CHcH2lc(c02c2H5)2 16. C4FgS02N CF3S02 H
17~ (CF3S02)2CHCH2CHCH2CH2Cl 2~ Br 18. (C4FgS02) 19- (C4F9s2)2cH2 20- (C4F9so2)2cHBr In all cases the xamples were left ln the air for 24 hours, Hard crystal-like, tack free particles resulted.
' _ ~3 --. - ~ '-lO~i;~8~) To 1.0 g each of the followlng silanes, 0,05 g of the catalysts Or Examples 9, 10, 12, 14 and 19 were added:
21-25~ H2C=C(CH3)Coo(CH233Si(ocH3)3 26-30- (CF3)2CFO(CH2)3Si(OCH2CH3)3 : 31-35, ~ Si(OCH2CH3)3 36-40O CH3Si(OCH2CH3)3 In all cases the silanes cured due to the activity of the :: catalyst.
: 10 EXAMPLE 41 ~ p~cp~yd ,'eth~y ~ A precondensate of 3(2,3-epoxy)pro~xydicthoxyf silane was prepared by mixing a flask set for distil-;- latlon, 16.5 gO 3~2,3-epoxy)propoxytrimethoxysllane in : -16O5 g. ethanol, 8.o gO water in 8 g. ethanol, and 1 drop of O.lN HClo The flask was heated to distill off volatiles to a pot temperature of 80Co ~ the residue cooled and diluted to a 60~ precondensate with methanol, To 10 gO
of this precondensate wa~ added 0O2 gO of trifluoromethyl , sulfonic acidO The precondensate was substantially fully .~ 20 polymerized after 16 hours at room temperature, ', EXAMPLES 42 - 44 -. To 10 g portions of the precondensate of the previous example (diluted to 40% in ethyl acetate) was "
added 1 molar percent of the catalysts Br ~ a~ (CF3S02)2CHCH2CHCH2CH
; bo ~ -CH=C(S02CF3~2 and `' C ~ ~ ( CF3S2 ) 2CH]2CH2 . The compositlons were cured 1n 30 minutes at 90CO
,..........................................................................
.

To 100 g portions of the precondensate of the prevlous example (40% in ethyl acetate) was added 5 molar percent portions of the catalysts:
a. La[(CF3SO2)2CH]3 b- Ni[(CF3S2)2CH~2 d. Pb[(CF3S02)2CH]2 e D Mn[(CH3S2~2CH]2 f. Ag(CF3S02)2CBr g- C4F9S02-N-SO2CF3 ho NH4(CF3SO2)2CBr, and i~ Pb(S2CF3)2 .

B In each case,-~Y~o was effected by heating at 90C. for 60 minutes and 120OCD for 30 minutes. The heat was suf-flclent to delatentize the catalyst salts.

_ ~ 5 ~

J
' Some materlals of the~e examples are auto-polymerizable, so examples were repeated without the catalysts for comparison.
In Examples 1 and 2 wlthout catalysts, the material had evaporated a~ter 1 day, and Example 3 evaporated after 4 daysO The materials o~ ~xampleR
4 and 5 became soft and cheesey after a few days and the material of Example 6 remained as a fluid~ Examples 45-52 remained as a ~luld after 7-1~2 hours at 90C.
- 10 me terms alkyl, aryl, and alkaryl as used in the practice of the present invention (excluding the defini-tions of Rf and R'f) also include those simple substitu-tions recognized as functional equivalents of those ; groups by the ordinarily skilled artisan in the practice of the present invention (such as -CH2CH2Cl~ S03 ~ , N02CH2CH2 ~
It has been found that at least some water must be present for the catalysis to occur~ but atmos-pheric moisture is quite sufficient. Only anhydrous conditions will prevent catalysis.

'

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A method of curing at least one silane compound sel-ected from monomers and polymers of the formuls XmSiR4-m wherein X is a labile group, R is a hydrocarbyl group resulting from the removal of a hydrogen atom from the carbon atom of a hydrocarbon or a hydrocarbon containing one or more heteroatoms selected from oxygen, sulfur, and nitrogen, and m is 2, 3 or 4 comprising curing said at least one silane compound by placing said compound into catalytic proximity with a catalytically active amount of a highly fluorinated aliphatic sulfonylic catalyst com-prising at least two highly fluorinated aliphatic sulfonyl groups attached directly to an imide or methylene group, and water.

2. The method of claim 1 wherein the highly fluorinated aliphatic sulfonylic catalyst is represented by the formula (RfSO2)-Q-(SO2Rf') wherein Rf and Rf' are independently highly fluorinated aliphatic groups and Q is selected from , and wherein R' is selected from hydrogen, chlorine, bromine, iodine, ammonium cation, and metal cation, R" is selected from hydrogen, chlorine, bromine, iodine, RfSO2, and alkenyl of 3 or 4 carbon atoms, and R3 is H, alkenyl of 3 or 4 carbon atoms or aryl of up to 20 carbon atoms.

3. The method of claim 1 wherein X is selected from hydrogen, halogen, alkoxy, aryloxy or acyloxy and R is selected from aliphatic groups of 1 to 18 carbon atoms and aromatic hydrocarbons of up to 10 carbon atoms.

4. The method of claim 2 or 3, wherein R' is hydrogen, R" is selected from hydrogen, chlorine, bromine and iodine, Rf and Rf' are perfluoroalkyl groups, and m is 3 or 4.

5. The method of claim 3 wherein the catalyst is of the formula:

(RfSO2)-Q-(O2SRf') wherein Rf and Rf' are independently a highly fluorinated alkyl group, and Q is a divalent radical selected from -NH- and -CHR1-wherein R1 is selected from Br, Cl, I, H, alkyl groups of 1 to 20 carbon atoms, alkenyl of 3 or 4 carbon atoms, aryl and aralkyl of up to 20 carbon atoms, and R5X, wherein R5 is an alkylene group of up to 20 carbon atoms and X is H, Br, C1, I, -O2SRf, -CH(O2SRf)2' , or -CY(COOR2)2 wherein R4 is H or C1 to C8 alkyl and n is 0 to 8, and wherein R2 is alkyl of 1 to 4 carbon atoms, or phenylalkyl, the alkyl group of which has 1 to 4 carbon atoms, and Y is H, Br, Cl, I, or NO2.

6. The method of claim 2 or 3, wherein the silane com-pound is an epoxy-terminated silane selected from and wherein each R6 is independently a divalent hydrocarbon radical of less than 20 carbon atoms, or a divalent radical of less than 20 carbon atoms the back-bone of which is C atoms which may be interrupted by individual atoms from the group of N and O, and O atoms in the form of ether linkages, m is 2 or 3, n is 0 or 1, and R7 is an aliphatic hydrocarbon radical of less than 10 carbon atoms, or an acyl radical of less than 10 carbon atoms.

7. The method of claim 1 wherein the silane is a copolymer of a polymerizable organic vinylic compound with 0.01 to 100 moles per 100 moles of organic vinylic compound of a vinyl trialkoxysilyl monomer of the general formula wherein R8 is hydrogen, methyl, or chlorine; and R9 is a divalent rad-ical selected from the group including , R10-, and , wherein R10 is a lower alkylene group having 2-6 carbon atoms.