DE1291121B - Production of embedding compounds that harden with platinum catalysts - Google Patents

Description

The invention relates to the use of mixtures of (a) liquid polysiloxanes, consisting of 10 parts by mole of RHSiO units (1) and 0 to 300 molar parts of RDSiO units (2) in addition to small amounts of chain-branching RSiO3 / z units and end-blocking R3SiOI / »units, in which R is monovalent hydrocarbon radicals, which are free from aliphatic multiple bonds means and where per molecule there is an average of at least 10 units (1); (b) 7 to 10.9 parts by mole a liquid α; -olefin hydrocarbon and (c) 0.02 to 1 mole part of one liquid α, # - diolefin hydrocarbon, the total molar parts of the existing terminal olefin groups of the hydrocarbon constituents within of 10 mol percent of the molar parts of the RHSiO units present, for preparation of investment compounds hardening with platinum catalysts.

These embedding compounds produced using the invention are for embedding electronic device parts and in general for use as Sealant suitable. Despite the lower Si content, they have the same good qualities Properties like the known embedding compounds consisting only of organopolysiloxanes and are also considerably cheaper.

Examples of monovalent hydrocarbon radicals R are methyl, ethyl, Isobutyl, hexyl, dodecyl, cyclohexyl, phenyl, biphenyl, benzyl, 2-phenylpropyl or Toluyl residues. Methyl radicals are preferred as R radicals.

The polysiloxane component (a) is a compound of the formula customary. The cyclic compound of the formula [CH3SiHO]. z is also known and suitable for making component (a). Analogous compounds of these and the like in which R is other than methyl radicals can be prepared by methods conventional in the organopolysiloxane field.

Copolymers of RHSiO and R2SiO units can be equilibrated of homopolymers of the two units in the presence of an acid catalyst can be obtained by conventional methods.

The component (a) can also contain small amounts of other units. This includes chain-branching units, such as RSiOs /, and end-blocking units of the formula R3SiOiI2, such as and (CH3) 3SiO112 The embedding compounds produced may also contain other constituents such as plasticizers, dyes, olefins whose double bonds are not terminal, excess α-olefins, fillers and organopolysiloxanes without SiH bonds. Of course, only in such amounts that the effectiveness of the embedding compounds is not impaired.

"Terminal olefin groups" are to be understood as meaning any carbon atoms linked to one another by a double bond with 2 hydrogen atoms on the terminal carbon atom. The best known is the vinyl radical, but this can also be of the formula correspond, as in α-methylstyrene or other substituted vinyl radicals.

Any el-olefins can be used as component (b). Examples of these are hexene-l, decene-l, 2-ethylhexene-l, styrene, octadecene-l or α-methyl styrene.

Any number of diolefins can be used as constituent (c) be e.g. Octaiden-1,7, 2-ethylhexadiene-1,5, decadiene-1,9, octadecadiene-1.17 or divinylbenzene. Mixtures of l-olefins and diolefins are also useful, as long as the mixture is liquid and the specified molar parts of α-olefin and l, ... -diolefin contains.

Platinum is used in any finely divided form, preferably but as chloroplatinic acid.

The platinum serves as a curing catalyst for the embedding compounds. Other suitable forms of platinum are platinum powder, platinum on charcoal or aluminum oxide or platinum complexes with olefins.

Usually only very small amounts of platinum are used because the platinum cannot be removed but is enclosed in the hardened embedding remain. However, there is no upper limit to the amount of platinum that can be used. as well the lower limit of platinum is also not decisive. But in general it runs cure too slow if less than 0.001 weight percent based on platinum on the weight of the investment material.

The hardening of the embedding compounds is presumably based on the reaction of #SiH bonds with the terminal unsaturated groups of the olefin constituents according to the following scheme: The monoolefins serve as plasticizers or solvents before curing. After hardening, they reduce the Si content and thus the costs of the embedding materials.

The α # diolefins serve as crosslinking agents, since each end of the molecule can react with a # SiH group.

The physical properties of the hardened embeddings can corresponding to the percentage of Si atoms that have reacted with a diolefin, can be varied. When this percentage is high, products become resinous educated.

With a lower percentage, elastomeric products are obtained, and with an even lower percentage of Si atoms that have reacted with diolefins gel-like products are obtained.

This percentage can be changed by changing the ratio of α-olefin to diolefin and / or the ratio of RHSiO to R2SiO units regulated will.

The embedding compounds can be liquids with low viscosity be that have excellent penetration, so that hereby Luttstellen completely filled in within small and complex circuit arrangements that cannot be achieved by more viscous material. The hardened ones Embeddings are essentially solvent-free if equimolar amounts of # SiH- and terminal unsaturated units are used. So that becomes the danger the formation of bubbles in the investment material during the hardening process is excluded, which is due to the presence of volatile solvents.

The embedding compounds are advantageously hardened by heating, where they are heated to 90 tris 170 C in one or more shutters. The temperature however, it is not critical as the curing reaction occurs even at room temperature takes place, but this takes about 5 days.

The upper limit of the curing temperature is determined by the thermal Determines the stability of the embedding compounds and their components.

The filler-free, hardened embeddings are generally transparent, elastomeric or resinous products that are in organic solvents or are insoluble in water. They give excellent protection for electronic devices Equipment parts at considerably lower costs than embedding compounds based on pure organopolysiloxane.

Example 1 55.6 g of a mixture consisting essentially of liquid Æ-olefins having 9 to 11 carbon atoms, of which 4 percent by weight were α # diolefins, were mixed with 24 g of the compound of the formula offset. This mixture contained essentially equimolar amounts of --SiH and terminal olefin groups. After adding 2 drops of a 0.2 molar solution of chloroplatinic acid in isopropanol with stirring, the liquid mixture was heated to 100 ° C. An exothermic reaction took place, as a result of which the reaction temperature was increased to 135 ° C. This was followed by 56.7 g of the mixture Heated to 150-C for 1 hour to form a soft gel.

Example 2 51.0 g of a mixture consisting essentially of α-olefins having 8 to 10 carbon atoms and containing about 6.7 percent by weight α, # -diolefins were mixed with 24 g of the compound of the formula added, which corresponded to approximately equimolar amounts of # SiH and CH = CH groups. After adding 0.1 ml of a 0.2 molar solution of chloroplatinic acid in isopropanol with stirring, the mixture was heated to 150.degree. After half an hour the reaction mixture had become viscous, even at the temperature of 1509C. After one hour the product was a clear resin.

Example 3 0.01 mole of the compound of formula (based on a molecular weight of 5194), 0.468 mol of tetradecene-1, 0.026 mol of liquid octadecadiene-1.17 and 1 10 5 mol of chloroplatinic acid were heated to 150 ° C. for 1 hour. A clear, elastomeric product was formed from the originally liquid reaction mixture.

Claims (1)

Claim: Use of mixtures of (a) liquid polysiloxanes, consisting of 10 parts by mole of RHSiO units (1) and 0 to 300 parts by mole of R2SiO units (2) in addition to small amounts of chain-branching RSiO: 3f2 units and end-blocking units R3SiO, h units, in which R is monovalent hydrocarbon radicals which are free from aliphatic Multiple bonds are, means and where per molecule on average at least 10 units (I) are present, (b) 7 to 10.9 molar parts of a liquid <z -olefin hydrocarbon and (c) 0.02 to 1 mole part of a liquid X5., - diolefin hydrocarbon, wherein the total mole fractions of terminal olefin groups present on the hydrocarbon constituents are within 10 mol percent of the molar parts of the RHSiO units present, for the production of embedding compounds that harden with platinum catalysts.