DE2846305A1 - METHOD OF CLEANING TECHNICAL SILICONE MATERIAL - Google Patents

Description

The invention relates to a method for cleaning commercially available Technical grade silicone materials.

E.g. in space travel but also elsewhere you need silicone materials, which must meet the following requirements so that they can be used under high vacuum:

a) A sample of the cured silicone material should not be higher Have a weight loss of less than 1% when heated to 125 C for 24 hours under a vacuum of at least 10 Torr;

b) the amount of condensable constituents obtained on a pane kept at 25 ° C. should not be greater than 0.1%.

Commercially available silicone materials with technical purity generally do not meet these requirements. The one from the Dow Silicone resin sold under the tradename Sylgard 184 by Corning Co. has, for example, a weight loss of 1.86% under the best test conditions described above, with o.5o% condensable at the same time Components are obtained.

The common silicone materials available commercially consist of a mixture of polymers with different chain lengths. The molecular weights of these polymers range from a few hundred to a few million.

Both the short chain polymers and the impurities are

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for the release of gaseous components through the commercially available Materials responsible.

So that these off-the-shelf materials are used under high vacuum these impurities and the short-chain polymers must first be removed.

In the United States, a method of cleaning silicone materials is available by I.T.R.I.I. and developed by NASA.

In this known method, those in the silicone materials contained small molecules by vacuum evaporation at a pressure of less than 10 Torr and by heating at a temperature of 15o C for 24 hours. This method has the major disadvantage that it is very costly, since it is very good Vacuum pumps and a vacuum container are required. Even with each cleaning process, only very small amounts of cleaned silicone material are obtained .

The present invention therefore aims to provide a method of cleaning are given by technical silicone, which can be carried out quickly and does not require expensive equipment.

According to the invention, this object is achieved by a method having the method steps specified in the characterizing part of claim 1.

The inventive method can be easily with little

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carry out equipment expenditure; the costs involved are low.

Process steps a to c can be repeated once or several times depending on the degree of purity one strives for.

The inventive method can be used in a variety of Use silicone materials, e.g. for polysilanes (liquids, fats) and organic polysiloxanes, which become elastomers or Resins are curable.

However, the method according to the invention is particularly suitable, and advantageous in cleaning crosslinkable (curable) silicone materials which are commercially available and a mixture of polymers of the following general structural formula are:

Si

R '

Si

R ¹

R.
ι
Si

ι
R.

Si ι
R ¹

R denotes a radical which is selected from the following group: methyl, ethyl, propyl, phenyl, monohalogen, dihalophenyl, -CF ₃ , -CF ₃ CF ₃ , -CF (CF ₃ ) _-, methoxy radicals and ethoxy radicals;

^{R 1} also denotes a radical which is selected from the following group: hydrogen, chlorine and bromine atoms and also Vi-

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nyl, hydroxy, isocyanate, amine, acyloxy, carboxy, carboxylate, Epoxy and

[S ΓΙΟ - radicals.

ρ and q are whole numbers.

In use, these polymers are crosslinked (cured) by acting ^{on the reactive groups R 1 with a suitable hardener.}

The method according to the invention is based on first of all dissolves the raw material. This is followed by a separation step, which is brought about by adding a reagent, in which the desired long chain species of polymer is insoluble. This separation step can be followed by a precipitation step be assimilated, in which the precipitated represents a phase which is immiscible with the starting solution. One such The cleaning process must not be compared to the one in GB-PS 1o 49 o38 described isolation procedure can be confused with which one a differential extraction and can only be used for a specific class of organic polysyloxanes, which contain terminal functional carbon groups. The present Process, however, does not relate to such organic polysyloxanes with terminal functional carbon groups.

As examples of solvents which can be used in process step a) are given: cyclohexane, aliphatic hydrocarbons, cyclo-

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hexene, xylene, benzene, toluene, mesitylene, triethylbenzene, methylene chloride, Chloroform, carbon tetrachloride, ethyl bromide, trichlorethylene, n-butyl chloride, chlorobenzene, o-fluorotoluene, 1,2-dimethoxyethane, 4-chlorotoluene, 1,2-dichlorobenzene, octylamine, methyl ethyl ketone, Diethyl ketone, ethyl acetate, propyl acetate, amyl acetate and cyclohexyl acetate.

As examples of non-solvent reagents, which can be used in process step b) are given: water, dimethylnaphthalene, 1,2-dichloroethane, 1,4-dibromobutane, Bromobenzene, 4-bromotoluene, methanol, ethanol, isopropanol, 2-ethoxyethanol, 2-isopropoxyethanol, 2-butoxyethanol, n-decyl alcohol, cyclohexanol, Benzyl alcohol, ethylene glycol, chloroethyl ether, dioxane, Diphenyl ether, aniline, acetone, cyclohexanone, ZT-butyrolactone, mesityl ether, Acetophenone, methyl acetophenone, ethyl format, isobutylphenyl acetate, Benzyl acetate, ethyl lactate, ethyl benzoate, diethyl phthalate, dibutyl phthalate, acetonitrile, 1-nitropropane, nitrobenzene and 1-nitrotoluene.

The collecting step c) can be carried out in a known manner, for example by Decanting.

Removing any remaining solvent and no solvent Representative reagent can be done by moderate heating. Heating in the temperature range of 60-1oo ° C is common well suited. Preferably, temperatures above 150 ° C should not be used to prevent premature curing. - q -

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The invention will now be illustrated by the following examples described in more detail.

example 1

Cleaning of commercially available silicone resin, which is called RTV 121 is sold by the Rhone-Poulenc company. It is a resin that is used as a basis for paints and Paint is used, e.g. the paint PSG 12o, which is sold by the Astral company.

50 g of the silicone resin are dissolved in 100 ml of toluene, then 100 ml of methanol are added to cause precipitation.

The mixture obtained in this way is emptied into a decanting funnel, the viscous phase is then removed after one hour.

This step is repeated twice, then the residues of the solvent and the insoluble reagent are removed by which is heated to around 60-80 ° C for two hours.

The purified resin obtained in this way can be used as a base material for the production of the paint PSG 12o.

The weight loss and percentage obtained on degassing and components condensable at 25 ° C were measured on a plurality of samples of the paint PSG 12o, which purified silicone

-1o-

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- 1ο -

resin (as described above) or non-cleaned, technical silicone resin.

The following measurement results were obtained:

Varnish PSG 12o with uncleaned silicone resin after curing at room temperature: weight loss 1.02%, condensable components o, 15%.

Varnish PSG 12o with cleaned silicone material · after curing at room temperature: weight loss o _f 70%, condensable materials 0.3%.

Example 2

Cleaning a silicone resin made by Dow Corning Co. is sold under the trade name Syigard 184.

50 g of the silicone resin were dissolved in 100 ml xylene. Then were 100 ml of methanol were added to precipitate.

The raised mixture was placed in a decanter funnel, and the viscous phase was removed after one hour.

This step was repeated twice, then the remainders of solvent and of insoluble reagent removed by heating at about 60 ° -80 ° C. for two hours.

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The purified resin thus obtained can be hardened by adding a hardener.

On various samples, which are made from, as described above, purified The weight loss and the percentage of when consisted of silicone resin and unpurified Sylgard 184 silicone resin were determined Degassing measured condensable materials obtained at 25 ° C.

The following results were obtained:

Uncleaned silicone resin Sylgard 184 after curing Room temperature: weight loss 1.86%; condensable materials o.5o%.

Purified silicone resin Sylgard 184 after curing at room temperature: Weight loss 0.4%; distinguishable components o, o9%,

Example 3

Purification of a silicone resin made by Dow Corning Co. is sold under the trade name Sylgard 182.

50 g of the silicone resin was dissolved in 100 ml of benzene, then were 100 ml of ethanol were added to precipitate.

The mixture thus obtained was placed in a decanting funnel, and the viscous phase was removed after 1 hour.

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This sequence of steps was repeated twice, then there were residues of solvent and non-solvent reagent removed by heating to about 60-80 ° C. for 2 h.

The purified resin thus obtained can be hardened by adding a hardener.

On different samples, which were cleaned as described above Sylgard 182 resin or consisted of unpurified Sylgard 182 resin, the weight loss and the percentage of components obtained during degassing and condensable at 25 ° C were measured:

The following results were obtained:

Uncleaned silicone resin Sylgard 182 after curing from 4 h at 65 ° C. and 24 h at 150 ° C.: weight loss 1.23%; condensable constituents 0.4%.

Purified silicone resin Sylgard 182 after curing at room temperature: Weight loss 0.4%; condensable constituents o, o7%.

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Claims (5)

Dipl. Ing. H. Hauck Dipl. Phys. VV. Schmitz Dipl. Ing. E. Graalfs Dipl. Ing. W. V; ε h η art Dipl. Phys. W. Carstens Dr.-ing. VV. Döring Mozartstrasse 23 Center National d'Etudes Spatiales βΟΟΟ Munich 2 129, rue de l'Universite Paris, France October 23, 1978 Attorney's file M-477o Process for cleaning technical silicone material Patent claims 1. Process for cleaning technical silicone material, marked through the following process steps: a) Dissolving the technical silicone material to be cleaned in a solvent suitable for this material; b) separating the solution thus obtained from a separate phase which contains the long-chain polymers by adding a reagent which is not a solvent for the long chain polymers; c) collecting the separated phase thus obtained; d) Removal of remaining residues of solvent and of the last-mentioned reagent from the phase separated off according to c). 2. The method according to claim 1, characterized in that the when Process step a) solvent used is selected from the following group: Cyclohexane, aliphatic hydrocarbons, cyclohexene, xylene, benzene, toluene, mesitylene, triethylbenzene, methylene chloride, - 2 - 909817/1008 Chloroform, carbon tetrachloride, ethyl bromide, trichlorethylene, n-butyl chloride, chlorobenzene, o-fluorotoluene, 1,2-dimethoxyethane, 4-chlorotoluene, 1,2-dichlorobenzene, octylamine, methyl ethyl ketone, Diethyl ketone, ethyl acetate, propyl acetate, amyl acetate and cyclohexyl acetate. 3. The method according to claim 1, characterized in that the reagent used in process step b), which is not a solvent, is selected from the following group: water, dimethylnaphthalene, 1,2-dichloroethane, 1,4-dibromobutane, bromobenzene, 4-bromotoluene , Methanol, ethanol, isopropanol, 2-ethoxyethanol, 2-isoproxyethanol, 2-butoxyethanol, n-decyl alcohol, cyclohexanol, benzyl alcohol, ethylene glycol, chloroethyl ether, dioxane, diphenyl ether, aniline, acetone, cyclohexane, methylacetophenone, Q -butyrolactone, mesylacetlhenone, Q -butyrolactone, methylacetlhenone, methylacetophenonone, Q -butyrolactone , Ethyl format, isobutylphenyl acetate, benzyl acetate, ethyl lactate, ethyl benzoate, diethyl phthalate, dibutyl phthalate, acetonitrile, 1-nitropropane, nitrobenzene and 1-nitrotoluene. 4. The method according to claim 1, characterized in that the technical silicone material to be cleaned consists of those materials is selected, which are represented by a mixture of polymers of the following general structural formula: 909 8 17/1008 R ι Si R ¹ Si t R ' R. O - R. I. t Si - Si ι I. R. R ' where R is a radical selected from the group below is: methyl, ethyl, propyl, phenyl, monohalophenyl, ^ CF
Dihalophenyl-, -CF-, -CF, CF3, -CF. , Methoxy radicals and ^CF 3 Ethoxy radicals, where R ^{1 is} a radical selected from the following group: hydrogen, chlorine and bromine atoms, as well as vinyl, hydroxy, isocyanate, amine, acyloxy, carboxy, carboxylate, epoxy and Radical; where ρ and q are integers. 5. The method according to claim 1, characterized in that the separating the separate phase obtained in process step b) is carried out in process step c) by decanting. 908817/1008