DE2255574C3 - Process for the preparation of silicon-containing polyformals - Google Patents

Description

2. The method according to claim 1, thereby forming low molecular weight oligomers. So should z. B. indicates that the silane in amounts of 25 in the implementation of a ^ s tetraalkoxysilane and a 1 to 50 mol percent, based on the total mol cyclic formals in a molar ratio of 1: 4 number of the formal-silane mixture, begins. average degree of polymerization of maximum 4 if only one alkoxy group reacts and a correspondingly lower average poly-

30 degree of merization when all four alkoxy

groups can be reached. However, it was found that during the polymerization it was the Alk article the invention isl a process for oxy groups of the silane used corresponding Production of silicon-containing polyformals is formed by dialkyl formal. Although dialkyl formalc Polymerization of cyclic formals in counter-35 as a very effective chain transfer agent in kaiwart of cationically active catalysts and of ionic polymerization of cyclic formals Silicon compounds. are known, the dialkyl formals occurring in the silicon-containing polyformals process according to the invention can be carried out more unexpectedly Polymerization of trioxane on its own wholly or at least partially from the or remove together with copolymerizable other 4 ° equilibrium, so that a higher poly monomers in the presence of linear, low, degree of merization is achieved.

Medium or high molecular weight siloxanes which contain two, three or four alcohol radicals attached to the silanes to be used according to the invention can be used according to the invention (CS-PS 118 939). Here, which should be able to be the same or different. In particular, the siloxanes by transfer in the form of terminals are preferred are silanes with three and, in particular, four alcohol residues built into the polyformal molecules. In the alkoxy and alkanes. Oxy radicals should generally be the number of carbon atoms. It is also already known that silicon-containing atoms are 1 to 20, and in the cycloalkoxy polyformals there are 5 or 6 radicals due to the copolymerization of trioxane ) -silicon compounds- 50 organic radicals will produce alkyl radicals with 1 to 4 Kiidungen (DT-OS 1570 561). In this case, carbon atoms or phenyl radicals are preferred. Polymers with chain-linked SiIi-silanes are for example: Tetramethoxysilane, Tctraciumatomen, but the production of the ethoxysilane used. Tetra-n-propoxysilane, tetraisopropoxysilaformals from simple silicon compounds is silane, tetra-n-butoxy silane, tetra-butoxy-2-silane, extremely cumbersome. '55 Tctra-tert-butoxy-silane, tetraisobuloxy-silane, Tetra-There has now been a process for the production of kis- (2-ethyl-butoxy) -silane, tetra-n-pentyloxysilane, silicon-containing polyformals by polymerization Tetrakis - (2,2-Dimethyl-propoxy) -silane, Tctracyclo of cyclic formals in the presence of cationic pentyloxysilane, Tetra-n-hexyloxysilane, Tctracyclo-effective catalysts and of silicon compounds hcxyloxy-silane, Tclrakis- (2-äthylhcxyloxy) -silane , Tegen found, which is characterized in that ^bu tra-n-heptyloxy-silane, tetraoctyloxy-silane. Tctraman at least one cyclic formal from the n-nonyloxysilane, tetra-n-dccyloxysilane, tetra group 1,3-dioxolane, 1,3-dioxcpan, 1,3,5-trioxc-n-dodecyloxysilane, Tetra-stcaryloxysilane, tetrapan, 1,3-dioxocane, 1,3,6-trioxocane and 1,3,6,9-tbenzyloxysilane, dimethoxydiphynoxysilane, metlitraoxacycloundecane in the presence of at least one oxy-triphenoxysilane , Tetraphenoxy-silane. Tctrakis-silane of the general formula 5 ^fi (2-methyl-phenoxy) silane, Tetraallyloxy-silane, tri-ethoxy silane -..., Triphenoxy silane, diethoxy-n-butyl ""''"silane, methyltrimethoxy -silane, dimethyl-diethoxy-polymerized, in which R is a hydrogen atom, silane, propyl-tri-n-butoxy-silane. Phenyl-tri-n-prop-

g ^ y - ,,, ΛΠ, Diphenyldiäthoxy-silan, Methyl-phenyl-di- by rapid cooling or by neutralizing

methoxy-silane. of the catalyst. When using a low catalyst

The silanes are expedient in amounts of satorkonzentrationscn will also arise

about 1 to about 50 mol percent, preferably favored by uncrosslinked polymers.

3 to 40 mol percent, in particular from 6 to 25 mol- 5 The polymerization can also be carried out continuously

percent, based on the total number of moles of the formula. Here you can z. B. the

Silane mixture, used. gangsmaierialien through a static mixer and

The polymerization is then pumped through a tubular reactor in the presence of 2 · ΙΟ "" ^1.

to 5 x l ° ~ ^l weight percent, preferably 1 · K) ¹ When highly viscous polymers are prepared to 1 ■ ΙΟ ^"1 percent by weight, in particular 1 M) -> io are, it is more advantageous to machine a screw

up to 10 ~ ^s percent by weight, based on the Gc- use. In such a machine you can use

total weight of the formal-silane mixture, one step to get to the end product, if

ionically active catalyst made. a neutralizing agent in appropriate zones

Examples of suitable catalysts are added protons and the volatile constituents removed acids, such as superchloric acid or pyrosulfuric acid, 15.

Lewis acid, such as boron trifluoride or tin tetrachloride, for some purposes they interfere with the

or their complexes, oxonium and diazonium neutralization of the catalyst with basic sub-

salts, such as hexarluoroarsenates, hexafluoroantimonates, punch resulting salts. In many cases you can

Hexafluorophosphate, piuoborate or perchlorate. len by iixiraction, for example with methanol. The very effective catalysts are particularly suitable. There are also difficult to escape

Lorries such as superchloric acid and its esters and raw materials that do not change during the polymerization

mixed anhydrides, such as methoxymethyl perchlorate, were set with extracted. It is particularly easy

learns. Butyl perchlorate, acetyl perchlorate or benzoyl- es mostly, the catalyst with the help of basic

nerchlorate to remove antimony pentafluoride, nitrosylhexafluoro- ion exchangers, »Ntimonat triphenylmethylhexafluoroantimonate and 25 The ci-

Other organic hexafluoroantimonates, triphenyl-containing polymers are well suited as hard

SSvlfluoroarsenat and other organic hexa-medium, thermoplastic polymers or

fluoroarsenate, already in amounts of less than elastomers and anorganic hen ^ rslar ^ gj ^ odei.

100 Dom initiate the polymerization. In comparison, fillers, especially glass fibers, are used in the application ZnXen catalysts are, for example, boron trituration as an adhesion promoter

ZoM or tin tetrachloride and their complexes may be useful, the catalyst after

considerably less active, so that they cannot be neutralized or de-

greater concentration must be used. ncn, so that the implementation of the Sil.uum-

^ß Whether in the process according to the invention low-atom reactive groups with enlsprc-

Molecular or high molecular weight polymers contain reactive sites of the Siibslratobcrna.hc

the speed depends in part on the speed at which it is applied. v-rfsh ^ n he

Save conditions. This is how the emergence is achieved according to the method according to the invention

S3 £ 3 * 5aX bfs insoluble products by high oligomers and polymers can be further

Krabü concentrations, high temperatures, and as plasticizers, as "" W "" ^^ g £

or long polymerization times are favored. Higher lubricant 1 or as lubricant additives al Hy

A degree of merization is also achieved when the hydraulic fluid or as a paint aid is used

non-cyclic formation formed during the polymerization. Through the use of various young people

Krmal WwähJnd, z. B. by distillation, given formals and silanes, vcr * h. ^ Motar «behavior

otherwise in vacuum, removed from equilibrium ms of cyclic formals and silanes, and variation

55 In this case it is advisable to leave all volatile 45 degrees of polymerisation

Punching after termination of the polymerization ab- J ^ t, ^ ^

draw. ,.

The polymerization is generally carried out in temperature. Vpr'nhren is through the

Twenigen Minutafbi, to several hours. The ^^^ ZZtLt ^ S, iÄ expedient Polymensaüonstcrnperatur and ^ J ^^ ¹ ^^ "S gLhromatographischer polymerization time required depends of course ^ ™™™""^^^ unreacted the type of used cycl.schen Formal silanes ^ -1 ^ of the dist .. ^ ^^ ^ _Hiifc and catalysts, but also of the molar ratio- 55 ^Amci ^. ^c _n ^ _t i _{on <viskosimete} r _S under user- '3' ^e '.

tert. Butyl perchlorate or acetyl perchlorate, as catalytic converter,

lysator and at starting temperatures between about 20 60 B e i s ρ i c 1 1

and about 50 ° C the polymerization mostly after VDioxepan were with 381 parts

Completed about 5 to 30 minutes or so far "^ ¹ ^, ' _{an is} ' _{cht and} at room temperature

advanced so that it can be canceled. ^ ™ ^ 3 ' ¹ ^ & with 3 ppm t-butyl perchlorate

When the emergence of insoluble polymer. »-" £ " _t * £ ⁿ Ä added. Of the

th is to be prevented, .st it is expedient to free the 65 (dissolved ^ rA hylenpg y , ^ ^^ _m _

ERS expectant Polymensat.onswarme continuously A ^"s att ewamte s" ig _{ht c GQO}

lead and the polymerization after reaching the ^ "^ f ^ ' ⁰ "? Stirred for hours. Thereafter

to cancel the desired viscosity, for example and the approach Z Munoen t,

5 6

was the catalyst by adding excess] - the reaction was decayed for another 1 hour at 80

likes to neutralize tributylamine. The volatile components up to 90 ^; C stirred and then worked up as

were described in Example 1 for 4 hours in a rotary evaporator. A colorless vis-

Heating to 90 ° C at 1 torr and stripped into a kos product with those set out in Table 1

Original caught with downstream cold trap. 5 dates received.

A colorless product with d; n in the table was e i s d i "17

belle 1 received the data deposited. ^p

1530 parts of 1,3-dioxepane were made with 76 parts

Example 2 Tetramethoxysilane mixed and at room temperature

1020 parts of 1,3-dioxepane were mixed with 381 parts of 10 with rapid stirring with 7 ppm of t-butyl perchlorate tetramethoxysilane and added at room temperature (dissolved in ethylene glycol dimethyl ether). After the reaction had subsided with rapid stirring with 5.6 ppm of t-butyl perchloride, the mixture was added at 80 rat for 1 hour (dissolved in ethylene glycol dimethyl ether). Stirred to 90 ^° C. and then worked up as described in Example 1 after the exothermic reaction had subsided. It was a colorless, stirred at 80 to 90 ° C for 1 hour. The batch was then worked up as in Example 1, with the very viscous product containing those in Table 1. Receive the specified data
it was found that with this one, with more catalyst “'s ο' e 1 8
polymerisation carried out a higher viscosity P

Product compared with the polymer of the by-204 parts of 1,3-dioxepane were 38 parts

game 1, was obtained (see Table 1). 20 Telramethoxysilane mixed and at room temperature

with rapid stirring with 80 ppm nitrosylhexa-

For example 3 fluoroarsenate (dissolved in a mixture of 6 () ° / o

In a mixture of 204 parts of 1,3-dioxepane ethylene glycol dimethyl ether and 40% 1,2-dichloro

and 38.1 parts of tetramethoxysilane were added to ethane). After the reaction subsided

Room temperature 2.5 ppm t-butyl perchlorate (dissolved in as stirred for another 2 hours at 80 to 90 ° C, then

Ethylene glycol dimethyl ether) stirred in. The meal is neutralized with methanolic sodium hydroxide solution

the mixture warms up and after 6 minutes and on the vacuum rotary evaporator, the volatile

55 ° C. It was then freed to 80 to 90 ° C. for 2 hours. There were 193 parts of one

heats and then the catalyst obtained by adding colorless polymer, which has a viscosity of

the stoichiometric amount of methanolic soda 30 4600 cP possessed. The starting substances were in

lye neutralized. The volatile components were polymers in a molar ratio of 11: 1 (1,3-dioxepane: Si

represented by rotary evaporation from the reaction gel),

mixed away and collected in a cold trap. _R. ■ 1 q

It was a colorless product with the in Ta- e 1 s ρ 1 e

belle 1 received the data deposited. 35,204 parts of 1,3-dioxepane were made with 38 parts

. . Tetramethoxysilane mixed and at room temperature

Example _{4 sc} h _ne llem stirring with 0.2 Vo tin tetrachloride

In a mixture of 204 parts of 1,3-dioxepane (dissolved in 1,2-dichloroethane). According to the cata-

and 38.1 parts of tetramethoxysilane were added to the room and the batch heated up in 6 minutes

temperature 6.5 ppm t-butyl perchlorate (dissolved in ethyl 40 from 20 to 57 ° C. It was further heated to 80 to

Lenglykoldimethyläther) stirred in. After 90 ° C has subsided and kept at this temperature for 2 hours,

the exothermic reaction was 1 hour to 80 to then the approach with triethylamine

90 ° C heated and then neutralized by adding a and on the vacuum rotary evaporator of

Excessive amount of tributylamine the catalyst frees the volatile substances. Stayed back

neutralized. The volatile components were replaced by 45 216 parts of a pale yellow product

Rotary vacuum evaporation from the reaction next was cloudy due to the precipitated salts

mixture removed and collected in a cold trap. some standing was clear and from the detached

It was found that with this one, with more catalyst, salts could be separated by decanting,

Polymerization carried out a higher viscosity It had a viscosity of 150 cP.

Product, compared with the polymer of the by-50_. . . _1n

game 3, was obtained (see Table 1). B e1s ρ ι e1 iu

. 148 parts of 1,3-dioxolane were combined with 38 parts

Example 5 Tetramethoxysilane mixed and at room temperature

816 parts of 1,3-dioxepane were mixed with 76 parts with 25 ppm of t-butyl perchlorate tetramethoxysilane with rapid stirring, and 55 (dissolved in ethylene glycol dimethyl ether) were added at room temperature. After 7 ppm of t-butyl perchlorate had been added to the catalyst with rapid stirring, the temperature rose in 14 co-dissolved in ethylene glycol dimethyl ether). After grooves from 22 to 76 ° C. In order to prevent crosslinking of the reaction at 80 ° C. for 1 hour, the polymerization was stirred at 90 ° C. and then worked up as described in Example 1 by adding 5 parts of methanolic sodium bicarbonate . A colorless, viscous liquor (5 percent) was broken off. The reaction product with the product listed in Table 1 was obtained from the starting substances and other data. ren volatile components by vacuum rotary valve. . steam released. 142 parts of a cloudy example 6 _ben product remained, which was used for further purification in 263

1224 parts of 1,3-dioxepane were dissolved with 76 parts of 65 parts of toluene and then under pressure of uii-

Tctramethoxysilane was mixed and filtered at room temperature soluble components. From the clear

with rapid stirring with 7 ppm t-butyl perchlorate were filtrate after evaporation of the solvent

(dissolved in ethylene glycol dimethyl ether) added. After 119 parts of a clear, colorless, water-soluble

Polymers obtained that have a viscosity of 2000 cP

owned. ■, ,, '

Example 11

232 parts of 1,3-dioxocane (1,5-pentanediol formal) were mixed with 38 parts of tetramethoxysilane mixture ¹ and at room temperature with rapid stirring with 12 ppm of t-butyl perchlorate (dissolved in ethylene glycol dimethyl ether). After the exothermic reaction had subsided, the mixture was heated to 80 to 90 ° C. for a further 2 hours and then neutralized by adding methanelic sodium hydroxide solution. The volatiles were removed by rotary vacuum evaporation. There remained 257 parts of a product with a viscosity of 500 cP, which partially crystallized after standing for a while at room temperature. The polymer obtained contained the starting materials in a molar ratio of 1,3-dioxocane: tetramethoxysilane = 8: 1.

Example 12

To 232 parts of 1,3-dioxocane and 52 parts of tetrpäthoxysilan 8.5 ppm of t-butyl perchlorate (were dissolved at room temperature with rapid stirring in ethylene glycol dimethyl ether). The batch heated to 69 ° C in 14 minutes and was then held at 80 ° C. for a further 30 minutes. After neutralization with mechanical sodium hydroxide solution the volatiles were removed by rotary vacuum evaporation. There remained 257 parts of a clear, colorless product with a viscosity of 400 cP, which after standing at room temperature for some time solidified into a solid, waxy mass. The polymer contained the starting materials in a molar ratio 1,3-dioxocane: tetraethoxysilane = 10: 1.

¹ example 13

To 204 parts of 1,3-dioxepane and 52 parts of tetraethoxysilane 2.4 ppm t-butyl perchlorate (dissolved at room temperature with rapid stirring in ethylene glycol dimethyl ether). The batch warmed to 55 ° C in 6 minutes and was then heated to 80 to 90 ° C for 2 hours. After neutralization with methanolic sodium hydroxide solution, were the volatile components are removed by rotary vacuum evaporation. 231 parts of one remained colorless, clear product with the data given in table 2.

Example 14

To 102 parts of 1,3-dioxepane and 80 parts of tetran-butoxysilane 10 ppm of t-butyl perchlorate were dissolved at room temperature with rapid stirring in ethylene glycol dimethyl ether). The batch warmed to 45 ° C in 10 minutes and was then brought to 85 ° C and stirred for 45 minutes at this temperature. Then was with methanolic Sodium hydroxide solution neutralized and the batch through vacuum rotary evaporation (up to 225 ° C, 1 Torr) freed from the volatile components. The yield was 115 parts of a yellowish, clear product the data given in Table 2.

Example 15

25 ppm of t-butyl perchlorate (dissolved in ethylene glycol dimethyl ether) were added to 204 parts of 1,3-dioxepane and 73 parts of propyltri-n-butoxysilane at room temperature with rapid stirring. After the reaction had subsided, the mixture was heated to 80 to 90 ° C. for 2 hours and then neutralized by adding methanolic sodium hydroxide solution. The volatile components were removed from the reaction mixture by vacuum rotary evaporation. What remained were 254 parts of a low-viscosity, pale yellow colored, clear liquid (see Table 2).

Example 16

To 102 parts of 1,3-dioxepane and 22.9 parts of methylphenyldimethoxysilane 9.4 ppm of t-butyl perchlorate (dissolved in ethylene glycol dimethyl ether) were added at room temperature with rapid stirring. The batch heated to 58 ° C. in 3 minutes and was then held at 70 to 80 ° C. for 40 minutes. It was then neutralized with methanolic sodium hydroxide solution. After evaporation of the volatile components in the vacuum rotary evaporator 113 g of one Colorless, clear product with the properties noted in Table 2 was obtained.

Example 17

In a mixture of 102 parts of 1,3-dioxepane and 34 parts of diphenyldiethoxysilane were at Room temperature by rapid stirring 9 ppm t-butyl perchlorate (dissolved in ethylene glycol dimethyl ether) equally distributed. The temperature rose with a simultaneous sharp increase in viscosity in 7 minutes from room temperature to 45 ° C. The polymerization was then carried out by adding methanolic Sodium hydroxide solution canceled and the reaction mixture in a vacuum evaporator from the volatile Shares exempt. 104 parts of an almost colorless, clear product with those given in Table 2 were obtained Properties preserved.

Example 18

74 parts of 1,3-dioxepane and 22.9 parts of methylphenyldimethoxysilane 110 ppm of t-butyl perchlorate were added at room temperature with rapid stirring. After the reaction had subsided, the mixture was heated to 70 to 75 ° C. for a further hour and then neutralized with methanolic sodium hydroxide solution. The volatiles were removed by rotary vacuum evaporation removed. There were 74 parts of a yellowish, clear, water-insoluble product with the Obtained a viscosity of 150 cP.

Example 19

204 parts of 1,3-dioxepane and 38.1 parts of tetramethoxysilane were added rapidly at room temperature Stir with 2.5 ppm t-butyl perchlorate (dissolved in

Ethylene glycol dimethyl ether) added. The temperature rose to 55 ° C. over the course of 28 minutes. This was followed by evacuation (final vacuum about 2 Torr) in order to remove methylal formed from the reaction mixture. The temperature fell to 40 ° C. and was then increased to 80 ° C. in 25 minutes by heating. The batch was then neutralized by adding methanolic sodium hydroxide solution and freed from the remaining volatile constituents on a vacuum rotary evaporator. 192 parts of a clear, colorless product with a viscosity of 190OcP remained.

Unexpected technical advantages of the method according to the invention compared to the method, d
CS-PS118 939 result from the following

pool test.

Based on

(ο

(Molar ratio 4: 1) mixed and at room temperature 3 ppm of t-butyl perchloral (dissolved in ethylene glycol dimethyl ether) are added with rapid stirring. Since the polymerization did not start, the batch was heated to 90.degree. But this was enough not yet to initiate the polymerization. Therefore another 3 ppm t-butyl chlorate were added, whereupon the polymerization started. The approach became more viscous and eventually separated in 2 phases. After 2süindiger polymerization at 80 to 90 ° C was cooled and the supernatant thin liquid phase decanted. The viscous lower phase (1160 parts by weight) was dissolved in 2320 parts by weight of ethyl acetate and neutralized of the catalyst with 20 parts by weight of tri-

10

butylamine added. A sample of the solution was taken for 3 hours to determine the polymer content 100 ° C / 15 Torr heated. What remained was 25% of a viscous, colorless clear product. This corresponds to converted to the entire batch, 870 parts by weight. Analysis of this product showed an Si content of 0.3%.

This test report shows that the octamethyltrisiloxane used in Example 1 of CS-PS 118,939 behaves like an inert substance under the conditions of example 1 of the process according to the invention and at most to a very slight extent Dimensions is built into the polymer, while in the process according to the invention polyformals with very considerable Si contents can be obtained.

Table 1

example Molar ratio
1,3-dioxepane:
Si (OCH ₄ ) ;, t-butyl
perchlofate yield Installation of
], 3-dioxepane
and Si (OCHj) ₄ Content of Si Mole percent
Methylal
related to viscosity in molar ratio built-in silane 4: 1 ppm C.'n) ("/«) cP 1 4: 1 3 94 4: 1 5.1 32 120 2 8: 1 5.6 91 3.9: 1 5.4 50 420 3 8: 1 2.5 88 8.7: 1 2.5 4th 500 4th 16: 1 6.5 94 7.7: 1 3.0 30th 1,800 5 24: 1 7th 94 ·) *) *) 2,500 6th 30: 1 7th 98 *) *) *) 7 800 7th 7th 94 28: 1 *) 9 19,000

*) Not determined.

Table 2

example Formally Silane Molar ratio t-bulyl
perchlorate
ppm yield
( ⁿ / o) Molar ratio
in the polymer viscosity
cP 13th
14th
15th
16
17th 1,3-dioxepane
1,3-dioxepane
1,3-dioxepane
1,3-dioxepane
1,3-dioxepane Si (OC, H ₅ ) ₄
Si (OC ₄ HJ ₄
C ₃ H ₇ Si (OC ₄ H,) ,,
CH ₃ (C ₆ H ₅ ) Si (OCH ₁ ).,
(C _e H _s ) ₂ Si (OC, H,) ₂ " 8: 1
4: 1
8: 1
8: 1
8: 1 2.4
10
25th
9.4
9 90
63
91
91
77 7.8: 1
about 5.5: 1
7.5: 1
8: 1
5.6: 1 200
250
100
600
5200

Claims (1)

a straight-chain or branched alkyl or patent claims: alkenyl radical, a cycloalkyl radical, an aralkyl radical or an aryl radical, R! a straight-chain or 1. A process for the preparation of silicon-branched alkyl or alkenyl radicals, a cycloalkyltigenic polyformals by polymerization of 5 radical, an aralkyl radical or an aryl radical, and η cyclic formals in the presence of cationic denotes an integer from 0 to 2. more effective catalysts and silicon compounds The silanes to be used according to the invention are fertilize, characterized in that simple and easily accessible connections. It you can get at least one cyclic formal from the was surprising that it is not only in the form of Group 1,3-dioxolane, 1,3-dioxepane, 1,3,5-tri-io end groups are incorporated into the polymer, oxepane, 1,3-dioxocane, 1,3,6-trioxocane and approximately according to their share in the output 1,3,6,9-Tetraoxacycloundecane are contained in the presence of min- starting mixture in the end product, at least one silane of the general formula "Depending on the proportion of silanes in the starting mixture, and depending on the applied SiR "(OR ') j" ₁₅ reaction conditions are different vis- polymerized, in which R is a hydrogen atom, kose or solid polymers obtained. Under otherwise a straight-chain or branched alkyl or the same reaction conditions arise with decreasing Alkenyl radical, a cycloalkyl radical, an aralkyl-containing part of the silanes, higher viscosity products, radical or an aryl radical, R ^{1 is} a linear When gfcicheni AnteiJ of the silanes, the viscosity may or branched alkyl or alkenyl radical, one of the polymers by changing the reaction Cycloalkyl radical, an aralkyl radical or a conditions can be influenced. This ν ar insofar Aryl radical, and η an integer from 0 to 2 surprisingly than had to be expected that with interpret. higher proportions of silanes as a result of transfer only