DE19507594B4 - Process for the preparation of silicone resins - Google Patents

Abstract

Process for the preparation of silicone resins having reduced alkoxy and / or residual chloride contents and defined reactivity, characterized in that, starting from the solvent-containing hydrolysis and / or condensation products of one or more organoalkoxysilanes of the general formula R _a Si (OR) _4-a (I), wherein R is independently, substituted and / or unsubstituted, saturated hydrocarbon radicals having 1 to 10 carbon atoms and a assumes values between 1 and 3, and / or their Teilhydrolysaten, during and / or after the separation of solvent by a quasi-solvent-free silicone resin melt at temperatures above 130 ° C water and / or steam is passed, wherein the alkoxy groups are completely or partially replaced by hydroxyl groups.

Description

The The invention relates to the preparation of silicone resins, in particular of methyl or methyl-phenyl-silicone resins, with reduced alkoxy and / or residual chloride contents and a defined reactivity. According to the invention, starting from the solvent-containing Hydrolysis and / or condensation products of one or more organoalkoxysilanes, while and / or after the separation of solvent by a quasi-solvent-free Silicone resin melt at temperatures above 130 ° C water or steam is passed.

The obtained resins find diverse Application, for example as a binder or coating agent.

The preparation of silicone resins based on the hydrolysis products of organohalogen and / or alkoxyorganosilanes by thermal and / or catalytic condensation in the presence of water-immiscible organic solvents is known (e.g. DD 228 550 ). The catalysts used are acids, bases or metal compounds. Preferred is the metal-catalyzed condensation which is carried out at higher siloxane concentrations at reflux temperature. This makes it possible to remove forming condensation water immediately azeotrope and to stop the reaction by dilution with solvent. The preparation of silicone resins with very low alkoxy and / or residual chloride contents is only possible to a limited extent due to the lack of uniformity of the silicone resins produced by these processes.

About the influence on the reactivity (crosslinking rate after catalyst addition) of the silicone resins is little known. Mainly reactivity and, associated therewith, the proportion of hydrolyzable functional groups contained in the end product are adjusted during the silicone resin synthesis (inter alia DE 41 32 697 ). For example, a higher content of alkoxy groups in the final product leads to less reactive resins, while the processing conditions on the silicone resin can be controlled by targeted adjustment of the OH group content.

US 2,832,794 teaches the preparation of OH-rich silicone resins by using low temperatures and low hydrochloric acid concentrations during hydrolysis.

US 3,489,782 also describes OH-rich resins by maintaining short residence times. Also by methods using solubilizers such as acetone, OH-rich products can be produced selectively.

ever higher the difunctional component in the silicone resins is the more elastic but also become reactionary these. This is why it is often necessary for special processing conditions the reactivity by an increase to improve the SiOH content.

task The present invention was therefore silicone resins, in particular Methyl and / or methyl phenyl silicone resins, which in addition to low alkoxy and / or residual chloride contents a variable adjustable level of reactivity and have an improved storage stability.

According to the invention it is possible to produce silicone resins having reduced alkoxy and / or residual chloride contents and defined reactivity by starting from the solvent-containing hydrolysis and / or condensation products of one or more organoalkoxysilanes of the general formula R _a Si (OR) _4-a (I), wherein R is independently, substituted and / or unsubstituted, saturated hydrocarbon radicals having 1 to 10 carbon atoms and a assumes values between 1 and 3, and / or their Teilhydrolysaten, during and / or after the separation of solvent by a quasi-solvent-free silicone resin melt at temperatures above 130 ° C water and / or steam is passed, wherein the alkoxy groups are completely or partially replaced by hydroxyl groups.

Under Silicone resins are understood to mean organosilicon compounds, composed of difunctional (D) and trifunctional (T) units are, with the proportion of T units mostly outweighs.

she contain Si-C bonds and production-related a share Si-OH and Si-OR groups in the molecule. Here determine salary and relationship the Si-OH and Si-OR groups and the degree of condensation the reactivity of the silicone resin.

When Organoalkoxysilanes are preferably monoorganotrialkoxy and / or diorganodialkoxysilanes and / or their partial hydrolysates are used, with methyl groups being used as organo groups. and / or phenyl groups and as alkoxy methoxy and / or Ethoxy groups are particularly preferred.

The Temperatures at which preferably passing at least 30 minutes of water and / or water vapor, are usually 140 to 160 ° C at atmospheric pressure, is preferred above the boiling point of hydrochloric acid worked in the system. The time during which water and / or water vapor is determined by the desired reactivity and is the longer, The higher the reactivity should be. The reactivity can be determined by gel time measurements, there is a short gel time for a high reactivity. Particularly advantageous is the passage of water and / or water vapor at elevated Pressure, for example above 2 bar, preferably between 3 and 5 bar.

The Passage is either by the after hydrolysis of the organoalkoxysilanes of general formula (I) and / or their partial hydrolysates oligomeric silicone resin or by the after condensation of the oligomers Silicones, usually in the presence of catalysts, silicone resin obtained during and / or after removal of the solvent, preferred by the quasi-solvent-free Silicone resin melt after removal of the solvent.

It is still possible as long as water and / or water vapor through the resin, until almost complete Replacement of the alkoxy groups by hydroxyl groups is carried out and so that the alkoxy group content goes to zero. This alkoxy group-free Silicone resins are outstandingly suitable for the preparation of silicone resin emulsions, since no disturbing alcohol elimination take place in the emulsion obtained can.

at the passage according to the invention of water and / or water vapor through the silicone resin is the mean molecular weight of the resin did not change significantly.

A preferred embodiment of the preparation of silicone resins according to the invention is as follows:
In a first step (1), the alcohols containing by reaction of organochlorosilanes, preferably methyltrichlorosilane, optionally in admixture with up to 30 mol% of dimethyldichlorosilane, with lower aliphatic, optionally up to 20 wt .-% of water, preferably methanol or Ethanol, resulting organoalkoxysilanes of the general formula (I) and / or their Teilhydrolysate, reacted with water, being added before or after the hydrolysis of organic, water-immiscible solvents, such as toluene or xylene, and form two phases. Then, after separation of the aqueous phase, in a second stage (2) present in the organic phase, oligomeric silicone resin, optionally after separation of a portion of the solvent, in the presence of catalysts to reach a predetermined melting point or a predetermined viscosity condensed , The catalysts used for this are usually the hydrochloric acid present in the system, iron (III) chloride, metal naphthanates and / or octoates.

The Passing water and / or water vapor through the silicone resin takes place either after stage (1) or after stage (2) while and / or after the separation of the solvent at temperatures above 130 ° C. After passing through water and / or water vapor it is both possible, that Silicone resin in solvent to solve and to condense further in the presence of known catalysts as well as to use it immediately, for example as a solution in everyone for it known solvents, such as toluene, xylene, benzines and the like. ä., or as a solid resin, for example in the form of flakes. Prefers is the passage of water and / or water vapor through a quasi solvent-free Silicone resin melt. The reactivity of the silicone resin is determined by means of Gelierzeitmessung determined.

By the method according to the invention, it is possible to completely or partially replace the silicon-bonded alkoxy groups (Si-OR) by hydroxyl groups (Si-OH) and thus decisively influence the reactivity of the silicone resins. Furthermore, the residual chloride content of the silicone resin is reduced. This makes it possible to adapt the silicone resins to certain fields of application, such as, for example, the production of mica insulating materials or emulsions, and at the same time the average molecular weight and thus to maintain the viscosity, in addition to an excellent storage stability, even of highly concentrated solutions, unchanged.

All silicone resins prepared were shelf stable at room temperature for more than 6 months. Determination of the analysis values OH _Si : FT-IR spectroscopy methoxy: FT-IR spectroscopy ethoxy: Reaction gas chromatography Molecular weight: Gel permeation chromatography gelling Time taken for a 55% silicone resin solution in toluene after addition of 1.2 wt% catalyst (solution of aluminum acetylacetate in ethanol / toluene) at 150 ° C to completely gel. Residual chloride: X-ray fluorescence

example 1

111.5 kg of monomethyltrichlorosilane and 13.2 kg of dimethyldichlorosilane reacted with a mixture of 78.1 kg of methanol and 8.7 kg of water. The resulting, partially hydrolyzed methylmethoxysilane mixture was intimately mixed with 45.8 kg of water in the presence of 107 kg of toluene. Obtained were an organic phase with 35% by weight of siloxane and a aqueous phase with about 10 wt .-% hydrochloric acid. The organic solution became concentrated in a column to about 80 wt .-% siloxane.

One Part of the concentrate was immediately in the presence of a ferric chloride catalyst at reflux temperature condensed. After condensation has stopped (dilute with Toloul to approx. 60 Wt .-% siloxane) was carried out by passing 550 g of water in the form of steam at about 140 ° C over a half a hour. The silicone resin (A) was obtained.

By the second part of the concentrate immediately became analog (A) water vapor passed [(silicone resin (B)] and then after re-dilution to about 80 wt .-% siloxane condensed with iron (III) chloride catalyst.

table 1 contains the results.

Table 1

Example 2

127 kg of monomethyltrichlorosilane were mixed with a mixture of 81.6 kg Methanol and 4.3 kg of water reacted. The resulting, partially hydrolyzed Methylmethoxysilane mixture was dissolved in 228 kg of toluene with 61.8 kg of water intimately mixed in a cycle. Was received one 20% by weight siloxane organic phase and an aqueous phase with about 20 wt .-% hydrochloric acid. The organic solution was concentrated in a column to about 80 wt .-% siloxane. By the concentrate was added 2 kg of water / h in the form of water vapor about 145 ° C directed. There were after 30 and 120 min. Samples taken and analyzed.

table 2 contains the results.

Table 2

Example 3

A concentrated silicone resin solution was used which corresponds to Example 1- (B), however using 112 kg of ethanol as the alcohol. 1220 g of this resin solution with 80 wt .-% siloxane and 12 wt .-% difunctional units were concentrated by distilling off the toluene to about 100% siloxane and then passed through 200 ml of water for 50 minutes at a temperature of 145 ° C. Excess water was removed with nitrogen and the resin dissolved 60% in toluene.

table 3 contains Details of the silicone resin before and after passing through water.

Table 3

Example 4

1270 kg, analogously to Example 1- (A), produced, condensed, toluolische Silicone resin solution with 55 wt .-% siloxane, were up to a bottom temperature of 150 ° C, which corresponds a Siloxankonzentration of about 95 wt .-%, concentrated, wherein from 140 ° C started with the addition of water. After reaching a bottom temperature of 150 ° C 40 liters of water were passed through the molten resin within 30 minutes directed. The bottom temperature dropped to 135 ° C. The remaining water was blown through nitrogen (1000 l / h), the resin with toluene on 55 wt .-% siloxane diluted back.

table 4 contains Details of the resin solution before and after passing water.

Table 4

Example 5

From 1165 kg 80% silicone resin solution (concentrated, prepared analogously to Example 1- (B)) was the Toloul abraded, starting from a bottom temperature of 140 ° C to the Achieving a quasi-solvent-free resin solution within of 2 hours, 35 liters of water were added.

table 5 contains Details of the resin solution before and after passing water.

Table 5

Example 6

975 kg 77% silicone resin solution (concentrated, prepared analogously to Example 1- (B)) were set to 100 % Siloxane concentrated, starting at 140 ° C over a period of 75 minutes 15 l of water passed through the bottom of the highly viscous resin melt were.

table 6 contains Details of the resin solution before and after passing water.

Table 6

Example 7

1 kg 80% silicone resin solution (concentrated, prepared analogously to Example 2) were concentrated to 100% siloxane, being from 145 ° C 100 ml / h of water passed through the bottom of the highly viscous resin melt were.

table 7 contains the results.

Table 7

Claims (9)

Process for the preparation of silicone resins having reduced alkoxy and / or residual chloride contents and defined reactivity, characterized in that, starting from the solvent-containing hydrolysis and / or condensation products of one or more organoalkoxysilanes of the general formula R _a Si (OR) _4-a (I), wherein R is independently, substituted and / or unsubstituted, saturated hydrocarbon radicals having 1 to 10 carbon atoms and a assumes values between 1 and 3, and / or their Teilhydrolysaten, during and / or after the separation of solvent by a quasi-solvent-free silicone resin melt at temperatures above 130 ° C water and / or steam is passed, wherein the alkoxy groups are completely or partially replaced by hydroxyl groups. Method according to claim 1, characterized in that that as Organoalkoxysilanes Monoorganotrialkoxy- and / or Diorganodialkoxysilane and / or their partial hydrolysates are used. Method according to Claims 1 and 2, characterized that as Organo groups methyl and / or phenyl groups are included. Method according to Claims 1 and 2, characterized that as Alkoxy methoxy and / or ethoxy groups are included. Method according to claim 1, characterized in that that the Temperature when passing water and / or steam 140 up to 150 ° C is. Method according to claim 1, characterized in that that this Passing water and / or water vapor through the after hydrolysis the organoalkoxysilanes of the general formula (I) and / or their partial hydrolysates obtained oligomeric silicone resin during and / or after separation of the solvent he follows. Method according to claim 1, characterized in that that this Passing water and / or water vapor through it after condensation the hydrolysis products of the organoalkoxysilanes of the general formula (I) and / or their partial hydrolysates obtained silicone resin during and / or after removal of the solvent he follows. Method according to claim 6 or 7, characterized that this Passing water through the quasi-solvent-free silicone resin melt after removal of the solvent he follows. Process according to claim 1, characterized in that at least for 30 minutes water and / or steam is passed through.