JPS5946543B2 - Heat-resistant organopolysiloxane composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to organopolysiloxane compositions with improved heat resistance.

A conventional method for improving the heat resistance of organopolysiloxanes is to add cerium compounds to organopolysiloxanes, but cerium compounds generally have poor compatibility with organopolysiloxanes, so they separate and precipitate. This has the disadvantage of defeating the purpose of improving heat resistance.

For this reason, as an organopolysiloxane, especially Si-H
Using an organopolysiloxane containing a small amount of bonds, cerium is added to the organopolysiloxane by adding a small amount of a cerium complex salt together with an aromatic hydrocarbon solvent and heating it to 280-290°C while blowing air. A method of dissolving or dispersing it has been proposed.

However, even with this method, the amount of cerium that is compatible with organopolysiloxane is extremely small, and it is difficult to manufacture products with a fixed cerium content with good reproducibility, making it difficult to sufficiently improve heat resistance. I can't. On the other hand, a method has been proposed in which a reaction product of cerium chloride or a cerium salt of an organic carboxylic acid and an alkali metal silanolate having three or more organosiloxane units is added to the organopolysiloxane.

According to this method, the reaction product exhibits compatibility with the organopolysiloxane, so that heat resistance is considerably improved, but satisfactory results are still not obtained. This method also has the industrial disadvantage that a large amount of precipitate produced must be removed by filtration. As a result of extensive research into improving the heat resistance of organopolysiloxanes, the present inventors found that (a) average compositional formula RaSi04-a (I) (R in the formula is a substituted or unsubstituted monovalent hydrocarbon group, a is 1
A composition consisting of an organopolysiloxane represented by (a positive number of ~3) and a reaction product of a cerium salt of a carboxylic acid and a silazane compound does not have the disadvantage of coloring and has remarkable heat resistance. They found that the present invention was improved and completed the present invention.

The organopolysiloxane used in the present invention is represented by the above-mentioned average composition formula (1), and may have a linear structure to a branched structure. Therefore, the value of a in the formula is a positive number from 1 to 3.

Substituted or unsubstituted monovalent hydrocarbon groups represented by R include alkyl groups such as methyl, ethyl, and propyl groups, aryl groups such as phenyl, and hydrocarbon groups bonded to carbon atoms of these hydrocarbon groups. For example, a trifluoropropyl group in which a hydrogen atom is partially substituted with rogen or the like is exemplified, but it is generally a methyl group. The above-mentioned organopolysiloxanes are particularly targeted to those with a linear structure that is liquid at room temperature, in which both ends of the molecular chain are trimethylsilyl, triphenylsilyl, vinyldimethylsilyl, or vinyldiphenyl. It may be any of a triorganosilyl group such as a silyl group, a hydroxydiorganosilyl group such as a hydroxydimethylsilyl group, and a hydroxydiphenylsilyl group.

Examples of cerium salts of carboxylic acids include cerium 2-ethylhexanoate and cerium naphthoate.
The silazane compound has the general formula (wherein R represents a substituted or unsubstituted monovalent hydrocarbon group, such as a methyl group, an ethyl group, a phenyl group, or a vinyl group, and n is O or 1-
(which is an integer of 5) is exemplified. The heat-resistant organopolysiloxane composition of the present invention is obtained by making the organopolysiloxane contain a reaction product of the above-described cerium carboxylic acid salt and a silazane compound, and such a composition can be advantageously obtained. You can do as follows.

That is, first, the above-described silazane compound, organic carboxylic acid cerium salt, and a small amount of water were added to a suitable solvent such as xylene, and the mixture was reacted at approximately 140°C for 1 hour, and then the organopolysiloxane was added. rear,
By distilling off the xylene content, the desired organopolysiloxane composition, such as a transparent silicone oil composition with significantly improved heat resistance, can be obtained. In the above method, the blending ratio of the silazane compound and the organic carboxylic acid cerium salt is 1 to 50 parts by weight, preferably 1 to 50 parts by weight, per 100 parts by weight of the silazane compound.
The content is preferably 0 to 25 parts by weight, and the proportion of cerium to the organopolysiloxane is such that the concentration of cerium in the final organopolysiloxane composition is 0.01 to 1%. desirable. In addition, when an organopolysiloxane composition having a cerium concentration of 0.1 to 1% is produced and this is diluted with the organopolysiloxane so that the cerium concentration is 0.01 to 0.1%. Also, an organopolysiloxane composition with significantly excellent heat resistance can be obtained. In the above method, the amount of water used may be approximately 10 to 50% by weight based on the silazane compound.

Note that this water is added to promote the reaction between the organic carboxylic acid cerium salt and the silazane compound. The organopolysiloxane composition obtained in this way has significantly improved heat resistance compared to conventional ones, but it may become colored or produce some precipitates at high temperatures such as 300°C. There is.

In order to avoid such disadvantages, it is sufficient to heat the organopolysiloxane composition to 230 to 250 DEG C. and blow air into it (aeration treatment) for about 1 hour. Furthermore, when performing this aeration treatment, if a small amount of methyl hydrodiene polysiloxane is added to the composition, an organopolysiloxane composition that is almost colorless and transparent and has excellent heat resistance can be obtained. next,
Examples of the present invention will be given below. Example 1 In a 500 ml flask, put xylene 150y1, hexamethyldisilazane 157, cerium octoate 40% by weight toluene solution 67, and water 37, and heat at 140°C.
The reaction was carried out by heating for a period of time, during which time unreacted water was distilled off as an azeotrope with xylene.

Next, 300 tons of dimethylpolysiloxane (viscosity 100 centistokes at 25°C) whose molecular chain ends were blocked with trimethylsilyl groups was added to this heated solution, and when the xylene content was completely distilled off, the cerium concentration was 0. A yellow transparent dimethylpolysiloxane composition of .2% by weight was obtained. 5 tons of this composition diluted 5 times with the dimethylpolysiloxane was collected in a 50 ml beaker and placed in an air oven at 300°C to examine its heat resistance. After 400 hours at the same temperature, the whole Although it was colored and some precipitates were observed, it did not gel.

On the other hand, when a similar heat resistance test was conducted on the dimethylpolysiloxane 5y, the entire product gelled in 5 hours.

Example 2 100f of the dimethylpolysiloxane composition with a cerium concentration of 0.2% by weight obtained in the previous example was mixed with 400t of the same dimethylpolysiloxane used for producing the composition, and this was heated to 250°C. Air was blown into this for about 1 hour while maintaining the same temperature to obtain a pale yellow transparent dimethylpolysiloxane composition.

This composition is 5t! When C was subjected to the same heat resistance test as in the previous example, no gelation occurred even after 400 hours, and no coloring or formation of precipitates was observed.

Example 3 Dimethylpolysiloxane composition 1007 with a cerium concentration of 0.2% by weight obtained in Example 1 was added with dimethylpolysiloxane 400f7 similar to that used for producing the composition.
, and methylhydrogenpolysiloxane-99
(Product name manufactured by Shin-Etsu Chemical Co., Ltd.) 2t and heated to 250°C.
The mixture was heated to a temperature of 100.degree. C., and air was blown into it for about 1 hour while maintaining the same temperature to obtain an almost colorless and transparent dimethylpolysiloxane composition.

When this composition 5f was subjected to the same heat resistance test as in Example 1, no gelation occurred even after 300 hours, and no coloration or formation of precipitates was observed.

Example 4 In a 500 ml flask, put xylene 1507, trisilazane compound 38y of the formula, 15 t of a 40% by weight toluene solution of cerium octoate, and 10 t of water, and heat at 140°C.
The reaction was carried out under heating for 1 hour, during which time unreacted water was distilled off as an azeotrope with xylene.

Next, 3007 g of diphenyldimethylpolysiloxane (25 mol% diphenylsiloxane units, viscosity 450 centistokes at 25°C) whose molecular chain ends are blocked with dimethylsilyl groups was added to this heated solution, and the xylene content was completely removed. When distilled off, the cerium concentration was 0.5
A yellow transparent dimethylpolysiloxane composition of % by weight was obtained. This composition was diluted 20 times with the diphenyldimethylpolysiloxane, heated to 250°C, and diluted with the diphenyldimethylpolysiloxane.
Composition treated by blowing air for hours (light yellow transparent) 5t
When the same heat resistance test as in Example 1 was conducted on
No gelation occurred even after 600 hours.

Claims (1)

[Claims] 1 (a) Average compositional formula RaSiO_4_-_a_/_2 (R in the formula is a substituted or unsubstituted monovalent hydrocarbon group, a
is a positive number from 1 to 3); (b) A heat-resistant organopolysiloxane composition comprising a reaction product of a cerium salt of a carboxylic acid and a silazane compound.